Can you check it for wear? Or get a pal to do so?
A worn chain/ cassette / chainrings can cost a fair bit to replace. Really needs a measuring tool to check but have a look at teh teeth on the chainrings – if they are hooked or worn looking odds are the drivetrain needs to be replaced. The other way to check is can you pull the chain away from the chainring at the front of the chainring? a rather subjective way of telling but if it will lift clear of the teeth at teh front ot the big ring its probably worn.
Check brake pads for wear
Check wheel bearings and head bearing – all should rotate freely without any play being obvious.