Laptop issues after update

Hi im trying to sort this laptop for my gf.

The Battery seems to have had issues since the update. Going from being fine, to now lasting very little time when not plugged in. It loses 3/4% per minute, then completely shuts down at 80%.
You plug it back in and its on 0%, charges gradually to 20% then magically claims its at 100% not long afterwards.

Ive done a systems diagnostics report which has failed continually on "System service checks". Ive done Sfc /scannow which reported no issues.

Has the Battery simply given up? Seems very odd timing & the laptop in general is much slower than before having used it previously. She wants to revert to the old windows, id rather get it sorted for her.

Thanks for any help & suggestions

What make and model is the laptop? Asking because the main laptop manufacturers have OEM forums, which are chock full of problems folks have been having since their Win10 upgrades. IF you go to the OEM forum for your laptop, you may very well find the solution.

Hi there, its a Samsung laptop NP-R540, cant seem to find a forum for Samsung laptops.

What i tried instead was to download Linux & test the system on a different operating system. The Battery still ran out pretty quickly, so im fairly sure thats the issue rather than Windows. Though i think the Laptops not having the easiest time running that either atm.

Thanks for the reply