Not sure if you still need help but, I will help now anyway. :)
Corrections are in bold. Some are simply spelling or grammar errors, such as commas in the wrong place.
1. Dame tu dirección para que te escriba.
Give me your adress so I can write to you.
Give me your address so I can write you.
2. Con razón nunca has podido aprender inglés. Nunca vas a clase.
No wonder you've never been able to learn English. You never go to the class.
No wonder you cannot learn English. You never go to class.
3. Ya nos habíamos ido cuando vino mi tío, ¿verdad?
We've already gone when my uncle came, haven't we?
We were already gone when my uncle came, right?
4.Cuando salí estaba lloviendo muy fuerte, así qes que me tapé la cabeza con un periódico.
When I went out it was raining very hard, so I covered my head with a newspaper.
Correct.
5. No habra clases mañana, así que no me despiertes temprano.
There won't be classes tomorrow, so don't wake me up early.
There won't be class tomorrow so, don't wake me up early.
6. No ha habido suficiente lluvia este verano, y se está secando todo el pasto.
It hasn't been enough rain this summer and all the grass is dying.
There isn't enough rain this year and all the grass is drying out.
7. No sé por qué he tenido tanta hambre toda la mañana. Comí bastante en el desayuno.
I don't know why I've been so hungry all the morning. I ate enough for breakfast.
I don't know why I've been hungry all morning. I ate plenty of breakfast.
8. ¿Va tu tío por avion o por tren?
Will you uncle go by plain or by train?
Will your uncle go by plane or by airplane?
Plain and plane are two different words. :)
9. ¿A qué hora cree Ud. que podrá acabar mi vestido?
What time do you think you'll be able to finish my dress?
At what time do you think you'll be able to finish my dress?
10. Estas son las flores más hermosas que jamás he visto.
These are the most beautiful flowers I've ever seen.
Those are the most beautiful flowers I have ever seen.
These are what is right by you, or in your hands.
Those are near you.
These flowers here = Estas flores aquí. OR Estas flores que tengo.
Those flowers there = Esas flores allí. OR Esas flores que usted tiene.
Hope I didn't confuse you. LOL