Question about assembling my own DIY AC Cable

Or is it better if the individual strands are a bit apart from each other and just insert them like this into the connector?

You can start with the exposed, stripped ends of the wire being a bit long (like 1/4 inch or 2mm longer than you need) and then use a pliers to grip them at the end and twist them together. The very end where you gripped the wires with the pliers will be screwed up so you cut the ends off so that all three sets of twisted wires are equally long and the ends look tidy.

You don't think it will create kinks or maybe even break? They are 1mm each in diamater 

thanks for the answer

I have done this many times so I probably have a better feel for what the wires can take before breaking than others who haven't made a lot of cables.  The idea is to twist them together just tight enough so they act like a single twisted wire and then you can feed them into the connector easier - they don't need to be any tighter.  Seven wires equaling an aggregate 5.53 mm square is just smaller than about 18 awg per strand.  Wires that size are more resilient than you might think, especially copper.  Just go slow and easy and you shouldn't break the individual wires.

Tyvm I'll do that

btw, do you have some suggestions how to remove the teflon surrounding each conductor? I peeled it off like peeling potatoes with a rather dull kitchen knife but there might be better ways of doing it.

The teflon is almost like chewing gum super sticky and elastic. I tried to simply make a 360 degree cut but somehow that didn't work and I didn't want to cut with too much foce risking to cut into the copper.