If I were you, I'd spend $4000 for Bitcoin and put them in a secure hardware wallet (Ledger Nano S only costs 70EUR, by the way). The rest $1000 is for altcoin with huge multiplier potential. My personal choice for now is WABI and BAT. WABI is currently sitting on 190 marketcap rank, defintiely undervalued given their consistent development. BAT is the same, while not severely undervalued like WABI, I think it should value more. Do your research for both coins and thank me later

I'm not a professional financial advisor. Do it with your own risk.