Back toin my college time, I learndays, I studied it for a year, but now I have forgotten all of ithem. Back in my college days, I studied it for a year, but now I have forgotten all of it.

"Back in" is the set phrase for this context. ("Back to" is used mostly for a location.) "My college time" is not a set phrase, so although it's understandable, it sounds odd to me. Another way to say this is "When I was in college." Because you are talking about taking a college course, "study" is a more precise word here and contrasts well with forgetting it.

Back toin my college timedays, I learned it for a year, but now I have forgotten all of ithem. Back in my college days, I learned it for a year, but now I have forgotten all of it.

If you took an actual French class (as opposed to studying it informally or picking it up passively), I would say: “Back in college, I studied it for a year, but now I’ve forgotten everything.”

Back to mywhen I was in college time, I learned it for a year, but now I have forgotten all of themeverything (I learned). Back when I was in college, I learned it for a year, but now I have forgotten everything (I learned).

You could also say "back in my college days." It sounds more natural than "college time," which I've not really heard before.

Back toin my college timedays, I learned it for a year, b. But now, I have forgotten all of them. Back in my college days, I learned it for a year. But now, I have forgotten all of them.

Back to myin college time, I learned it for a year, but now I have forgotten all of them.what I learnt. Back in college, I learned it for a year, but now I have forgotten what I learnt.

Me too 😅

I think I will pick it up again someday. I think I will pick it up again someday.

Nice use of this phrase!