Sorry, but there is no easy solution to this.
The most likely case is that your keyboard is failing -- as those in laptops are not designed to be durable or long-lasting. I maintain 3 laptops, all over 5 years old, and all have had their keyboards replaced at least once.
And given that your PC is (apparently) no longer under warranty, you would have to pay to have the work done as well as for the replacement keyboard.
For repair estimates, you would need to contact an HP Repair or Service Center.
If you live in the U.S., here is a link to the HP Service Repair Centers:
https://www.service-center-locator.com/hp-hewlett-packard/hp-hewlett-packard-service-center.htm
If you live outside the U.S., here is a link to HP Service Centers, by Country/Region: https://support.hp.com/in-en/service-center
Good Luck