My average typing speed (English) is 20 wpm and highest I got is 28 wpm. What should I do? I want to type faster like 40-50 wpm.?

I started 3 months ago with typemaster and after finishing full course I am using By the time I a getting slower and getting demotivated. I am using Dell kb216 keyboard. I bought it 2 days ago. before that i was using another frontech keyboard. Is something wrong with my keyboard?
Update: After 2 months of posting this question and practicing, my average is now 40+ wpm and highest is 51 wpm (in
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