As others have pointed out, I'd recommend:
- please rename "amateur" to something more positive. no customer wants to be called an amateur
- Increase prices for the pro tier
- Improve your "pricing plan" page, take a look at other (more successful) SaaS products and change button labels accordingly. Just take the best things from their landing pages!
- create a proper comparison matrix / table for all the plans
- visually de-emphasize the free tier, and focus on the 3 paid plans in your comparison table. people will always buy the middle option, so you can increase the price of the "best" option by a lot in order to anchor your value
- add features which are available only in "pro" and "pro plus", e.g. support, direct email to developer, etc!
- maybe build a mobile app for this? it seems like something that could be nicely integrated into a mobile-first experience. you could make it exclusive for pro users