I don't really have confidence about bitcoin because I believe the upper limit of bitcoin will not be much higher.
what do you mean by "upper limit"? the total supply? if that is the case then you are wrong. the final supply is fixed at 21 million and that is a consensus rule which will never change.
Nework (NKC) is the first blcokchain project I have heard, that's why I choose to invest, but how to recognize a good project and how to choose a potential coin？
it seems like a completely random useless token that you saw in an advertisement randomly online and fell for it. i don't see any real potential in it.
Can anyone share your strategy about investing cryptocurrency?
the most important thing to remember is that you should never trust the things you read online from random people that are not known to you who are advertising some altcoin.
instead you should learn how the altcoin market works so that you can trade altcoins and make profit on your own.