It's looking good Mats, the nice thing about soldering is you can desolder, clean up and try again. Flux is a necessity as well as the surface you're going after being clean. I did some soldering on the Jeep this weekend. Not much but just enough to put a grin on my face. I need to get a new tip for my gun.
Our old Master Watanabesan did a great series on soldering.
https://www.modelersalliance.com/list-of-the-masters/44-yasuyuki-watanabe/64-soldering-method-1-tools
https://www.modelersalliance.com/list-of-the-masters/44-yasuyuki-watanabe/67-soldering-method-2-basic-technique
https://www.modelersalliance.com/list-of-the-masters/44-yasuyuki-watanabe/68-soldering-method-3-slight-applied-technique
Our old Master Watanabesan did a great series on soldering.
https://www.modelersalliance.com/list-of-the-masters/44-yasuyuki-watanabe/64-soldering-method-1-tools
https://www.modelersalliance.com/list-of-the-masters/44-yasuyuki-watanabe/67-soldering-method-2-basic-technique
https://www.modelersalliance.com/list-of-the-masters/44-yasuyuki-watanabe/68-soldering-method-3-slight-applied-technique