Complete the conversation, putting the verbs into the past simple or present perfect simple ​

Greetings, Anna! I am happy to hear from you! And i want to advice you something what i do know about that.
To my mind, people become vegetarians because of couple reasons - because it's fanshionable right now and because they do not want to hurt the animals. But, all over the world there are lots of examples, that vegetarians can keep fit. They do some drinks with protein or just find it in eggs or breeds. 
But i think teens should not do it because we are growing up and we should get every kind of vitamins. 
I hope, my advices will help me. 
Take care of yourself

If he goes with me, I will be happy.
If Mary works hard, she will be promoted.
Andrew will buy drinks, if i cook dinner.
Mom will present a computer, if her children study well.
Olga will write an essay, if Julia helps her.
My brother will enter the university, if he studies diligently.
Tom and Garbrielle will ride a bicycle, if the weather is good.
If Porter stays to London, he will go to National History Museum.
If i finish school year with good marks, I will go to the seaside this summer.
If dad hear that we don't sleep, we will be punished.