I was playing minecraft with no lags. But when my friend joined, i started to lag i couldn't do anything but i pressed middle X to unfreeze it i got back on moving, but same thing happened repeatedly in like every 5 secs

Thank you for your report!
We're tracking this issue in MCPE-142692, so this ticket is being resolved and linked as a duplicate.

If you would like to add a vote and any extra information to the main ticket it would be appreciated.

If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.

Quick Links:
📓 Bug Tracker Guidelines – 💬 Community Support – 📧 Mojang Support
📓 Project Summary – ✍️ Feedback and Suggestions – 📖 Game Wiki