You may say 少し日本語をしゃべるけど、上手じゃありません。 (sukoshi nihongo wo shaberu kedo, jouzu ja arimasen) which would translate into "I speak a little Japanese, but I am...
'totemo konde iru.' Totemo has kind of fallen out of daily speech though. I would use Sugoi konderu ne With a fellow College studentOr Sugoku konde imasu ne With a person of higher status
It depends on context, what you are describing, etc. For example, to say food that you have just eaten is very good, say the following: Oishikatta!To thank someone for food that they have either...