Here is my last attempt. I felt like adding solder afterward is it the way to do it.
all comments welcomed

Thanks

 

so the oil on my fingers could be the reason why the tin was not sticking or encompassing the wires?

That could be one of the reasons. The wire could also have already had some grime on it. If the solder wasn't bonding to the wire, it's either due to surface contamination, improper wetting, or too much solder.

so what kind of flux to get for that?

I use liquid rosin flux. I bought a liter in the mid-1990's and still have most of the liter left.

yes I have acetone . how much to apply and when?

Use a cotton ball dampened with acetone and wipe off the grime on the surface. It'd be best to wear a latex glove because acetone is hard on your skin.

Apply whenever you need to remove grime and just before attempting to solder.

 

I felt like adding solder afterward is it the way to do it.

You shouldn't need to add more solder after soldering the joint. You should be heating the wires and applying solder until it flows over the entire area. I couldn't see where you were applying the solder or if it was actually flowing.

You applied too much heat because not only did the insulation melt, it also turned black.

Wearing gloves would let you handle the wires and not contaminate them with oil from your hands.

You need to get a stand with arms with alligator clips so you can hold both wires and be able to apply some pressure on the wires with the iron tip.

Like this (one arm shown):


If you're having so much difficulty soldering, maybe you should go with a crimp option.

 

Crimp connectors/tools:

 

Here's a video of someone soldering stranded wire (not tinned). Skip to the 6:00 minute mark.
https://www.bing.com/videos/riverview/relatedvideo?q=stranded wire solder breaking&mmscn=stvo&mid=556D5551DA0B6E536090556D5551DA0B6E536090&ajaxhist=0

He's not even using a tinned tip or flux (but is wearing gloves). But his technique is okay. He interleaved the wires before twisting. I don't think that's necessary. He's also holding the spool of solder, like you were. I don't get that because I use 1-pound spools and that would be very inconvenient. I break off a length of solder to use. If it's more than a few inches long, I wind it around my fingers to make a small loop(s).

A better video at 0:45: https://www.bing.com/videos/rivervi...3E3F35818A58B66E65AB3E3F35818A58B6&ajaxhist=0

Not wearing gloves, didn't use flux, didn't use tinned tip (but put a blob of solder on it), just twisted the wire. He put the iron under the wire, applied solder from the top, and didn't move the tip around.

 

That could be one of the reasons. The wire could also have already had some grime on it. If the solder wasn't bonding to the wire, it's either due to surface contamination, improper wetting, or too much solder.
I use liquid rosin flux. I bought a liter in the mid-1990's and still have most of the liter left.
Use a cotton ball dampened with acetone and wipe off the grime on the surface. It'd be best to wear a latex glove because acetone is hard on your skin.

Apply whenever you need to remove grime and just before attempting to solder.

hi could the black also come from the rubber insulator I touched with the iron?Like can melted rubber travel on -in the liquid solder?

the little bottle is it the kind of flux that would help solder travel?

- I took note of you advice and watched the videos. good learning. putting the iron under will already help me see better among other things.

 

hi could the black also come from the rubber insulator I touched with the iron?

Yes, but why would you touch it with the iron? It's not what you're trying to solder.

the little bottle is it the kind of flux that would help solder travel?

That's the type I'm using. The Amazon price works out to just under $400/liter. I paid around $20/liter (albeit 30 years ago).

Rosin flux isn't exactly what I'd call no clean.

I took note of you advice and watched the videos. good learning. putting the iron under will already help me see better among other things.

The tip on your iron is still way too big.

 

and at the end of a work do you guys like using electrical tape to insulate the solder . what are pros and cons of electrical tape vs shrinking protector vs? other ways Thanks

to insulate soldered connections (connector pins etc) use heat shrink. do not use electrical tape - it is a temporary measure. if you leave it on long enough it will become lose, come off and leave sticky mess.

short soldering video:
3 Ways to Solder the Same Microchip | Different Techniques, Same Result