First of all your improvement is great. For me, I have been cubing for 4.5 months with CFOP and avarage 17.78 . In order to improve faster in my opinion is doing about 150 solves a day that might seem alot but as you get faster you would get motivated to practice more. From my experience, I was stuck at 20 seconds just 1 week ago , I was learning lookahead, olls but no luck then I did a 150 solves a day and my times dropped really fast. Btw what cube do you use. I had a qiyi warrior W. Then I bought a thunderclap v3 m and some lube and ... I don't know what to say. JUST DO IT