Trade BTC/ETH to Altcoins?

Hi, I only have BTC/ETH in my portfolio but I have a question. Is a good move to swap a part of BTC to Altcoins for example in this "bullrun" and with the little time left to the halving. I mean, I know that BTC is more secure, but in the bullruns the ALT go higher faster than btc or I am wrong? Likewise I dont know in which alt I would invest... I am a little noob on this World and I see that every body loves BTC more than nothing, and obv is the most secure coin but like I said i dont know if is the best idea to hold all of my portfolio in BTC and ETH or I have to diversificate more. Thanks and sorry for the dumbs questions...