Seems you are new to the forum. Please have a meaningful topic in the "subject" field when you open a new thread. Also, mention the purpose of your writing such as IETLTS, TOEFL or GRE. Again, include the full prompt with your essay as many others do so that others would provide you with more relevant feed backs.
Nowadays, liviing standardhas been improved day by day and technical breakthrough help fercilitatefacilitate people's life.
..."Nowadays" and "day by day" clash with each other. Also, this sentence does not flow well.... Also, avoid expressing your ideas in a complicated manner with too many big words. What's more important is clarity and a beautiful flow;
With rapid advancement of technology, the quality of peoples lives are being improved almost day by day.However, parents shouldn't underestimate the impact of cellphone on their children,
You need a link between your previous line and this. You talk about the cellphone all of a sudden without any reference to what you said earlier. Bridge the two ideas!