First of all - welcome to BC !
If an external keyboard works but the fitted one doesn't, then you have a problem with the keyboard. If turning it off, turning it upside down and giving it a good shake doesn't fix the problem then you are reduced to (1) using an external keyboard, (2) If it is purely the numbers, then you can get USB keypads, or, (3) you can replace the keyboard.
Laptop keyboards are not normally very expensive items, it is just the fitting of them. This can range from dead easy to a nightmare ! The best thing to do is to go to YouTube and enter the make and model of your laptop plus the word 'keyboard'. You are almost certain to find at least one video showing you what is involved. If you do this and then feel the task is beyond your confidence level approach a local repair shop - but get a quote from them first first.