Hi, please try resetting your router by unplugging it at the wall for 30 seconds, then plugging it in and powering it back on, then restart your Galaxy A53 to address any temporary software issues that might be a contributing factor.
Following the reset, head to Settings > Connections > Wi-Fi > Tap the 3 dots in the top right > Advanced, and switch off 'Turn on Wi-Fi automatically'.
If the issue occurs while you're using a certain app then please try heading to Settings > Connections > Data usage > Mobile data only apps, and check to see if any apps are listed here that might be disabling your Wi-Fi when in use.
