You have a few grammatical errors but the main thing that I see is that your sentences all seem very choppy. I know there's a word limit, but I would try to put some sentence variety in there.
Also, you're telling more than you are showing. Like, you say "was" a lot and you should try to avoid saying that too much.
The sun was shining too brightly as I tried hard to keep my eyes open.
Could be changed to
I struggled to keep my eyes open as the sun beamed brightly on my face.
I would try to put more like, emotion I guess into it. Instead of saying
My face was burning, from the heat of the sun and the sinking feeling in my chest.
Maybe you could say something like
My face burned as embarrassment overwhelmed me.
Something like that, I don't know.
Good luck!
Christine Gales