It's because small means küçük, not young. Young means genç. So if you say 'you are small' to someone you actually imply that he/she is small in age/size or "very" young. I wouldn't say it means only "You are young." because then you wouldn't use the word küçük to express it. You can just say Sen gençsin.
Ufak is a synonym word for küçük and it means exactly the same thing. When we talk about kids we usually say 'ufaklık' which can be translated as 'the small one' I believe.
Where is the small one? -> Ufaklık nerede?
peki, çok teşekkür ederim :).. And in case there is no synonim for something, then we could translate it the way i suggested? for example sen guzelsin (i have an english keyboard) could be used as you are beautiful + you are a beutiful one + you are the beautiful one? (if there is a synonim for that also then i hope you could understand anyways what i am trying to ask :)
When they say "sln", in the tables the "l" in the middle means one of four vowels to be determined by 4-way Vowel Harmony. It took me a while to get used to that. I kept wondering what happened to the "l" and how do we know which vowel to put, but you look at the last vowel that is already in the word and that decides which to add.