Comment by amelius

The main insight you need to have:

The things you want to solder need to be at a minimum temperature for the solder to properly flow.

Parts with a lot of metal attached to it will need more time to get hot. Most notorious are pads connected to a large (ground) plane.

If the solder does not flow properly because of this, increase the time of contact between your soldering iron and the items, add a small amount of solder to the tip to increase contact area. Or use a heat gun in your other hand or a preheater. Or buy a soldering iron with more power.

Flux will help too.

Use a fan to draw the fumes away from you, at a minimum. If you do this on a daily basis, get a fume extractor.

There are many more tips on the internet. The first thing I mentioned is the most important one, imho.