Student or Learner
For colloquial way to express :
1. kleenix (tissue)
2. adhesive bandage (band-aid)
3. Kotex (sanitory napkin)
What others words that I should learn in common?
There are a lot of brand names that have become commonly used for the generic item. You can find more be doing a web search for "brand name as generic name." But be aware that these brand names are not sold everywhere. For example, I don't know Kotex.
That's probably because you're a male. Kotex is sold in Australia and New Zealand - it is a feminine hygiene product. Back in the old days when there were only two or three companies that sold these types of products, "Kotex" became synonymous with "sanitary napkin." Of course today there are a dozen different competing brands of this product line and "Kotex" no longer has that instant recognition factor.
Anyway, the technical term for the phraseology OP is looking for is "proprietary eponym." Some of the more common examples in the US are:
plastic wrap/cling film - Saran Wrap
facial tissue - Kleenex
photocopy - Xerox
cola-flavored soda pop - Coke
transparent adhesive tape - Scotch Tape
hook-and-loop fabric fastener - Velcro
adhesive bandage - Band-Aid
flavored drink powder - Kool-Aid
digital video recorder - TiVo (often used as a verb, as in "Don't tell me how the ballgame ended, I TiVo'd it and haven't watched it yet.")
petroleum jelly - Vaseline
I hear that in Britain all vacuum cleaners are "Hoovers."