To be sole developer.. what struggles did you face ?. Did you do something like hiting the head on walls when your code broken. ?

No head-hitting, just lots of googling, so, docs reading and so.

The struggle was not knowing whether I'm heading to the right direction. Is this the best way? Am I wasting my time looking there? Am I growing professionally or just tip-toeing in the same place? Or maybe it's antipatterns I'm learning and going backwards?

I'm more of a r sole developer

Being a sole developer has always been my thing, not by choice though... just the way things work out.

Not having anyone to bounce ideas off makes for a struggle in its self, but at the same time having to dig deeper into many areas gives you a better understanding of how things work, except that has the issue where you become the source of information for everyone else.

When I do get to a point that I hit a brick wall, it's coffee O'clock and I go for a walk and stop thinking about the problem.

Also, be sure to use git or some VCS... saying it because not all devs use this, so when ever you skrew up royally, you can just reset and try another approach.

The code is rarely the issue: it's just a logic problem, and it always has an answer; often multiple. You can also clean up and build things in any way you please, as well as you please. So the code is never really an issue.

The issue is almost always management: if you're the only developer, that means they aren't, so they don't (and can't) understand what you do, why it's difficult, or why things can take time. They also tend to hold all of this against you.