You need to read up. A lot.
Also, never trust anyone for investment advice. Make sure you get to a level where you can form your own analysis on when to sell, buy, or HODL.
Your knowledge will guide you here all through out, as a beginner you should make a lot of efforts to learn everything about cryptocurrency and most importantly here in forum. You can read a lot of information here, and over time you will ranked up and you can join now in signature campaign and start making money.