Today I'm going to go to the gym.

Today I'm going to go to the gym.
I will do exercises for bottom of body my lower body, especially for my feet foot's.
On Monday I did exercises for top my upper body - . It's the chest and arms.
I have to do exercises correctly to increase strengthen/build my muscles.

Hi Dimitri... you use "lower body" or "upper body" when you are talking about exercise in the gym.

"Build" or "strengthen" my muscles is more natural than "increase" my muscles.