Its my senior year and I’m starting to take 3 AP Courses (Environmental - Art History - BC Calculus).
For those courses in specific, do I have any chance to finish on time and practise well? or am I too late and should forget it?
My studying potential in a day normally is 4-6 hrs! I’m really interested in these subjects (especially for the Art History and Environmental I think I can study them as delights 
)
Starting new AP courses will not help you get into college at this point. The main thing now is to keep up your grades in the classes you are taking. IF you want to take the others, that is up to you…see if the colleges you are interested would give you credits for those courses.
But if you think about it, normally you would take those courses over a school year (in HS)…you have what you are taking and you want to add 3 high level courses? Does not sound like a good idea.
I would think about what you want to study…if STEM oriented, then yes it would be good to have background in Calculus.
Environmental - Art History - BC Calculus
APES is one of the easiest APs to self-study. If you have a good memory and have a good background in science, you should be fine.
AP Calc BC: What’s your previous math class? Did you take AP Calc AB? AP Calc BC is second semester of college calculus. You should be able to self-study it in 3 months if you are dedicated enough and have solid calc 1/ap calc ab background.
AP Art History: I wouldn’t recommend it. A lot of materials to go over.
@jason861101 , Your answer gave me some hope finally in this life thanks mate!
Though I’ve not taken AP Calc. AB however we covered the topics of calculus until the integration by parts in school. So I think I’m qualified for Calculus BC. Or isn’t it? :-?
Not even close. You still have many topics in AB to cover.
Depending on your background and interests, Art History is possible, but you really need to have some background in the subject since there is a boatload of works of art to memorize.