Phone keeps losing home Wi-Fi

Coverage, power saving or an individual device may be responsible.

Do not factory-reset a router speculatively or indiscriminately disable Wi-Fi security or a firewall. Get permission before changing someone else’s network.

Test the phone near the router. Check whether another device disconnects at the same time.
If every device is affected, check the router and internet line. If only the phone is affected, briefly turn its Wi-Fi off and on.
Restart the phone. Temporarily test without a power-saving mode you enabled, then restore your preferred setting.
Forget the network only if you know the current password. Do not reset all network settings as a first step; other saved connections may be lost.

Test after each step and stop when the issue is solved. Checkmarks are not permanently saved.