Keys double typing.

I am currently using an Apple MacBook Air from late 2018, and when I type, sometimes my letters repeat.

For example, when I type the letter X, it'll type the same letter like three times, so it'll turn out to look like "Xxx," and when I try to space it, it spaces like three times, so I don't know if my keyboard has any dirt under it or if my keyboard is messsed up. As you can see, when I typed "messed," you see it doubles types lots of "S." I need help. How do I fix this?