Tig & stick welding is harder but this is a good intro to welding metals👌

At 4:15, the instruction manual says "use a good quality soldering iron" but neither the manual nor the video mentions the importance of tip size, shape, and material; nor does it warn of the prevalence of cheapo, junky tips made of steel being sold on the internet (They should be made of copper for fast, efficient heat transfer, but not bare copper which tends to pit and corrode from the effects of molten solder and flux; high quality copper tips are typically plated with chrome or similar metal that resists solder, except at the pointy of end of the tip, which needs to be plated with iron; iron allows solder to wet to it but will resist the dissolving and corrosive effects of solder. Tips should not be highly magnetic throughout, only at the iron-plated end of the tip. If you buy tips from ebay, amazon, aliexpress or temu, theyll almost certainly be junky tips made of garbage metal. For that matter, pointy conical tips are apparently the defacto standard for tip type included with a new soldering station, even though "chisel" tips are often a better match to the work being done; you'll have to buy them separately).

That's a terrible solder joint at 0:37. There's no mechanical connection, you can't hold the wire still enough by hand, and the solder will fracture as it solidifies. Never reheat solder without adding a bit more solder and flux. Don't heat the joint too long after you stop feeding solder.