After trying some canned routines in several different occasions, I came to the conclusion that I experience most difficulties with fluff talking. I cannot keep the conversations going and they seem to die every 5 minutes and then I have to bring up a completely different subject.
What can I do to keep the conversations going and what are good subjects to talk about. And how can I build up tension in this mid-game?

5 minutes or so is about the lifespan of a topic it seems. You are going to have to "weave" your topics. Try to piggy back what you are talking about to give yourself more material. If you want to go to something else unrelated just use "Oh that reminds me..." even if it isn't related in anyway this works super well.

The reason it works it because as humans our attention spans and the way we think can be kind of random. We can be driving down the street going to get a burger and think... "Oh I almost forgot I need pet food." It is just how the human mind works. So if you run out of stuff in a topic just use... "Oh that reminds me" and go on to something else you want to talk about.

I personally love telling stories from my life about various things I've done, places I've been, what I believe, family, etc. They are easy to relate to for others listening and generally get a lot of commentary.