Can't play with friends and very slow

Hi,

My son has Nintendo switch and has had Minecraft since he got it (Dec 2019). Recently it has been running very slowly and won't allow him to play with friends on it. I've deleted all his worlds, hard reset it, deleted and re-installed. This is causing him some distress as it's his favourite game to play with friends. There are no issues with any other game on the switch. I contacted help and they said they couldn't help and I should raise a bug issue. I've no idea if I've done this right or not. Please let me know if you need more info. Please help us. 

Thank you & kind regards

Samantha