Crash server every 30 minutes

Good evening I play with a friend since yesterday on a server Aternos in 1.13.2 except that it lag a little good until then it's normal we're on a free server but the problem is that every 30 minutes the server crash and so every 30 mins I have to raise. It's pretty embarrassing so I wanted to know if we can remedy that or it's normal. Thank you for your answer in advance. PS: Sorry if my english is bad I use a translation software