And I keep on hearing about and seeing people writing a bunch everyday. So I thought I could do. Guess I'm still an amateur.
I know it's very tempting to compare what you do with others but I think this might be the root of the problem: There are a lot of factors going into somebody's output and you hardly know about those when somebody mentions how often they update/how much they write so comparing your output to theirs will lead to unsatisfying results in many cases.
Like, maybe these people have more time on their hands than you? Maybe they don't need to research as much for their current story? Maybe they are writing less detailed? Maybe they can handle more wpm because they're naturally faster or have trained themselves? Maybe the many chapters they post are just shorter than yours?
There are many more possible reasons why somebody might be faster than you and this doesn't (necessarily) have anything to do with them being more professional. So don't use them as your measure for how much you should write, just use what you're comfortable with as a measure. If you want to write more, then maybe try to identify what could be holding you back and find ways to change that. Like ...
Could it be that you procrastinate too much? Then maybe set a dedicated time just for writing and put away your phone or cut off your internet connection for that time.
Could it be that you're writing at the wrong time (since different people will be more productive at different times)? Then maybe try writing at a different time.
Could it be that your hand speed is too slow? There are exercises you can do to train that so maybe try a few. Or if you're unsure about this, try to do a test to measure your possible wpm first.
Could it be that it's not the actual writing but the preparation? Like, maybe it could help you to plan the scene/chapter you want to write that day out first. I've heard from quite a few people who will be faster in the actual writing stage when they do that.
Anyway, as others have pointed out already: Consistently writing more is something that needs you to spend a lot of time and effort. It's something that is hard to do from one day to the other so just take your time with it. Maybe raising your writing goals by a little each week or month might be better than raising it by a lot at once. Of course, this also depends a bit on the person. Just try out different things and see how it works for you.