You're right--this is a nice, long essay, but I can at least help you get started!
"According to the Oxford Advanced Learner's Dictinory "renaissance" means a situation when there is new interest in a particular subject, form of art after a period when it was not very popular."
I think this was probably a typo, but "Dictionary" is spelled wrong. My first suggestion would be to run the spell-check on the essay in your computer. ;-) Also, something seems to be missing from the sentence; should it be ". . . subject or form of art . . . "? The comma seems to be out of place in that phrase.
"The other meaning of "renaissance" in the same dictionary stands for the Italian renaissance."
Capitalize "Renaissance" in the "Italian Renaissance" reference, since you are naming a particular epoch.
"However, there is an other period which is called "The Twelfth Century Renaissance" which played a significant role in Europe's history."
It might sound a little smoother to say, "However, another period also played a significant role in Europe's history. It was called "The Twelfth Century Renaissance."
"Afterwards, about 7th and 8th centuries, Muslims attacked the Mediterranean and the trade and communication between East Europe and West Europe ceased."
Insert "the" in front of "7th", then delete "the" before "trade." How about "Eastern and Western Europe"?
"These two significant events culminated in a rural society, quite different from the Roman Empire which was an urban civilization."
How about: ". . . quite different from the urban civilization of the Roman Empire."
"With the changes, a new economic system was founded, feudalism."
You could say ". . . a new economic system called feudalism was founded" or "feudalism became the new economic system throughout Europe." Or something like that.
"Within the lord's castle and land, there was a perish church, which systemized the life."
You mean "parish" rather than "perish." (Look up the meaning of "perish", as applied in this sentence; I think you'll be amused.) :-))
"Until the revival of trade, during feudalism, people lived in a small world which was the castle."
". . . the small world of the castle" would be better.
"Many members of the feudalic society were illiterate and they knew nothing but work."
It should be "feudal" rather than "feudalic."
"For example, by declaring, "People who suffer in this world will find happiness in the presence of God", the Church made the poor peasants feel better and work within the feudalism."
Delete "the" before "feudalism." Also, the comma should go inside the quotation marks.
"However, feudalism like many other economic systems came to an end with the revival of trade."
Insert a comma after "feudalism" and "systems."
"Christianity, while leading the social and economic life in many aspects, directed the lords, chivalries, and other eager feudal warriors to the lands of Muslim."
Either say "the lands of the Muslims" or "Muslim lands."
"By this way, the Church was planning to expand the christianity to muslims and also to capture the Holy lands."
Say either "In this way" or "By this method." Delete "the" before "Christianity," which you need to capitalize, along with "Muslims."
"Crusaders were on the scene of the Medieval Age."
"Crusaders played a prominent role in the Medieval Age" would sound more scholarly. :-)
"Crusades took place from the beginning of the 11th century."
"The" should be the first word in the sentence. I would also advise giving an ending date, or range of dates.
"The raids of the Crusades did not reach the targets of the Church, while it played an important role in the revival of the trade."
I think "did not accomplish the goals" would be more clear than "did not reach the targets." Also, I would change "while it" to "although they." And delete "the" in front of "trade."
"Furthermore, the Crusades provided an advantegeous position in the Mediterranean Sea for Christians against the Muslims, weakened the papacy, and lastly, the aristocrats, in other words, the land lords lost power because of the Crusades."
"Advantegeous" should be "advantageous." I would change "and lastly, the aristocrats, in other words, the land lords lost power because of the Crusades" to "and weakened the power of the aristocracy throughout Europe." I'm pretty sure the reader will be aware of the definition of "aristocracy." Also, it isn't necessary to mention the Crusades again; once is enough.
"Trade transformed the feudal society which is rural, into an urban civilization like the Roman Empire."
I would say "the rural feudal society." I try to avoid using "which is" as much as possible when I write.
"The new markets, and the new inventions such as plow increased the agricultural production."
Delete the comma. Insert "the" in front of "plow" and delete it from in front of "agricultural."
"The peasants searched for new lands, at the end, forests and also marshes transformed into agricultural lands."
How about: "In a search for new land, the peasants transformed even forests and marshes into agricultural properties."
"The peasants were in better conditions by the help of the trade and the urban life; consequentl, the population increased during this period."
I suggest: "Trade and urban life improved conditions for the peasants, and as a consequence, population increased during this period."
"Aristocrats freed their peasants, rent hem lands in order to gain money, because money was important again, and the lords were eager to take part in this new life style."
I'm not sure if my idea is historically accurate, but if it is, I would suggest: "Money, rather than barter, was now the coin of the realm. The lords were eager to participate in this new prosperity; they freed their peasants and rented them land for monetary payments."
"In line with these changes in the feudal life style, a new group of people appeared in the scene of Europe, merchants."
I would move the merchants to the middle of the sentence: ". . . a new group of people--merchants--became important on the European economic scene."
"The revival of trade and the revival of cities made the capital important, the importance of land decreased."
Begin the sentence: "As the revival . . .
"The changes during the 11th century, changed the structure of Europe."
Delete the comma. Also, I suggest not using "change" twice; maybe you could substitute "innovations" for the first one.
"If it these changes had not taken place, Europe probably would be a different society, maybe a society which is based on agriculture."
Again, I suggest deleting "which is." You don't need it in this case.
Your essay shows that you've done some in-depth research and have a good grasp of your subject. My time is up for now, but I would be glad to take a look at the rest of it tomorrow.
Meanwhile, best wishes to you!