Today

Today I´ve given a presentation in the secretary´s office, the final project for my degree in electrical engineering. Now I´m waiting for them to give me a date, so that I can defend it.

Later (better: afterwards) I was to working out at the gym. My trainer gave me a special training routine, called "Crossfit" , and when I finished these exercises, I didn´t feel good. My eyesight got blurry and I almost fainted. I think this happened because I didn´t eat enough food at breakfast.
Before doing hard exercises, it´s important eat food that absorbs slowly like whole-grain cereal.

Could someone correct my little writing?

Great work!  Focus on smaller sentences instead of run-on sentences with lots of commas. It will make your writing more clear.

Today

Today I presented my final year project for my degree in electrical engineering in the secretary´s office. Now I´m waiting for them to give me a date so I can defend it.

Later, I was to working out at the gym and my trainer gave me a special training routine called "Crossfit". When I finished these exercises I didn´t feel well, my vision was a bit blurry and almost I fainted. I think this happened because I didn't eat enough food for breakfast.
Before doing hard exercises it´s important eat food that has slow absorption like whole grain cereal.

Could someone correct my little writing?