Why my battery drain so much without using phone

Hi @dazzlermumtaz

Try disabling the mobile data setting and check if that resolves the problem.

Go to Settings → Network and Internet → Mobile Network or in quick settings press the ↑↓ icon.

Be aware that disabling this setting means that the phone can no longer access the internet or send/receive mms messages (texts with videos/images).

If it does resolve the problem then there's an app that may be accessing the internet in the background unbeknownst to you. The trick is to find out which one.

It could also just be that the battery is starting to fail and needs to be replaced. Here's a teardown video that may help with its replacement. Search online for QM50 battery to find battery suppliers that suit you best.