I have around 2k USD of btc and I wanted to swap it for something but I can't decide whether to buy eth or Solana both seem extremely promising in the far future.
Do you want to sell Bitcoin and buy Ethereum or Solana? If you hold Bitcoin for a long time then you can earn a lot of profit from investing in Bitcoin. Both Solana and Ethereum are very good to invest. You can invest in both Ethereum and Solana. Of your $2000 dollars, put 50% in Bitcoin and 30% in Ethereum and 20% in Solana. Many other people have suggested here, you can invest according to the advice that seems good to you.