You can lift the affected keys off the keyboard to get at the key contacts. Clean with solvent spray cleaner under the rubber contacts.
The keys can be replaced by positioning over the plactic hinges and pressed home until it clicks into place.
If this doesn't work you will need to replace the keyboard.
Keyboard replacements are available on the Internet, I replaced one from Yall Store for approx. $60
Go to www.yallstore.com