Blue lines on text

Why are there blue lines under my text?

I’ve looked into this, and in most cases, they are talking abut when they’re dictating words. I’m not dictating. I’m sliding-to-type, but when I’m writing messages to people or writing in the notes app, sometimes every word in a sentence is underlined blue even though there’s nothing wrong with it. It will suggest correcting “to” as “too” or “top” or “Too.” It does the same with “of”. Or it’ll suggest a random capital word in the middle of a sentence or words that I never use like “stork” or “AB’s”. I don’t get it. I’ve turned on and off most of the settings under keyboard but it doesn’t change anything. I’m getting really annoyed at this so please fix this or tell me how to fix it.