How can I repair the non-functioning keys of my notebook?

Suddenly, six different buttons on my notebook (TOSHIBA Satellite C670-199) stopped working. - First I had the last Windows update in suspicion, because after such an update, there was ever a similar problem. - But when I put an external keyboard on it, all keys worked again. - I then carefully lifted the keys from the notebook, but that did not help. - For a repair, the notebook is already too old, - who has a good tip for me, which I could try myself.

Poorly ok:

https://www.ebay.de/...3363886725

Thanks for the hint, but I do not buy anything on the internet!

Ok, everyone has their principles.