It`s more than likely its the keyboard matrix bellow the marked keyboard symbols has worn out Alex, especially if the laptop is around two to three years old Alex.
You can buy a replacement keyboard from ebay for as little as £12, where it simply involves you to disconnect a flat ribbon cable under the base of the flat type keyboard with low profile keys.
Then connecting the new one, taking about ten minuets of your time to do.
Just simply get the model number of the Lenovo laptop from the underside of it the searching ebay with replacement keyboard along with the brand and model number in a search queries.