As developers we make these common mistakes, but in order for us to grow we need to learn from our mistakes right? So here's a shortcut of it.
Learning new Frameworks
In learning frameworks, common mistakes we make and trust me when I say this: we sometimes skip over things like the basics. For example you're new to javascript (haven't done this but I often see in the community) they instantly go to frameworks without even knowing the basics of javascript. And in the long run they would encounter problems. So probably best to learn the basics first then you can go explore once you understood it.
Not reading the Documentations
Now this I learned the hard way (haha), even though you got lots of experience and understanding (how to code and how it really works [the gist of it]) you tend to skip through the parts, developing applications can be so complex that these documentations may help you save time. Sometimes the only solution to your bug or problem is in the documentations. Also now that's what I fully rely on that video tutorials on youtube or something. These Documentations are highly accurate so give it a chance.
Difference between SPA and MPA
I once used an SPA for a blog for a client which is very wrong because SPA isn't SEO friendly. Web Applications that handle dynamic content and in need of marketing or improve traffic are in need of SEO. The only time you should use SPA is when building landing pages or something really simple hence 'Single Page Application', E-Commerce / Blogs and other CMS are bad for that. You can still implement SEO for SPA but it is only for one page.