Aternos is a free service and therefore limited in the resources that can be used to run the servers. If you need more RAM with better performance and you are able and willing to pay, you can try out our paid service exaroton: https://exaroton.com.How to join an Aternos server?
Connect to your server – Aternos Connect to your server To connect to your server, copy the server address and enter it in your Minecraft client, as a new server or with "Direct Connect". You can find the server address on the server page.How to make Aternos server 24/7?
give yourself a command block place it then type inside the command block "/setidletimeout 100" then change the command block to repeat and always active so it'll repeat the command forever, making it online forever if it has 1 player..