> It was lead-free soldering tin with flux included.

Flux core solder is crap. It doesn’t contain enough flux to begin with and since it’s inside the solder, it can’t actually do the work it’s supposed to. You need to apply flux separately before soldering, and lead-free solder used to be harder to work with. That’s the leading mistake I’ve seen frustrate beginners.

Steady hands aren’t a requirement unless you’re doing very complex repairs like threading wire through a BGA grid. You’re supposed to use the surface tension of the solder to snap the component’s pins to the PCB pads. After you snap two corners to the pads, you can just glide a tip with some solder over the rest of the pins and the heat and flux do the rest of the work (the flux’s main job is actually changing the solder’s surface tension to make this easier and more predictable).