I had an issue with my keyboard similar to this- not a lenovo laptop but a dell.
started with my space bar (which you really need) Tried all the items such as cleaning, etc. It worked for a while but then stopped - I had to replace the whole keyboard, bought one online and then brought it in to be replaced. It was a bit cheaper that way but still cost a bit of money.
If you know a good computer repair place - I'd call them and ask their suggestion -they should be able to give you a quote on the what the repair would cost.