Java OutOfMemory

Hey there, I have a LobbyServer running Paper (PaperSpigot-“4c7641d” - 1.8.8) and everytime the Server is on for a duration of like 10 minutes the TPS go down drasticallly and crashes. The Stack:
I hope you can help me.

EDIT: I have 2G given to it but there are typically around 2 - 3 players online (me and a few others to test the server)

Kind regards,