Did I lie to my friends about how long I have been studying?
I'm not sure why you think this is an important issue. 

"It's complicated" is enough of an answer if you want to be honest.

But small lies in this context do no one any harm and may ease social situations. Some simple questions such as the ones you get aren't worth the effort of composing a complete and complex answer. It's complicated. Say more to those you think need to know more or those you are closer to. 

Don't sweat it. 

If there were any issue at all in such a situation it would be overselling your skills to those you need to work with on a joint project. But you don't seem to be erring on that side here.