PS. I forgot to write about this, but here goes:

Several days ago one of my neighbours visited my place, and we took a look at the entrance hall. He has considerably more experience of building and renovating. And he was kind of a suggesting to tear down the entire extension part, and then re-build it. In a way that would be easier =) As I am keeping some parts of the old structure, it also means that there are hardly no straight lines nor exact sharp angles. Each and every piece I have to measure individually, to make them fit to their place.

For example, in the third picture there is that new support post, which is light in colour. It is 4" by 4", the bottom resting on a replacement part I did yesterday, and the upper part supporting an old horizontal beam. Now, if I were building a completely new extension part, I could first measure, cut, and intall all the vertical pieces, and then place a horizontal beam on top of them. But now I first have to measure the exact distance between the lower beam and the upper beam, and then cut the 4"x4" to that same length.

I missed one post, accidentally cutting it 5mm too short. Some of the others were initially 5mm too long, but that was easy to correct by cutting just a tiny bit away. When they fit nicely, I was using a small sledge hammer to move both the lower and upper end to their desired positions.

Like, the roof is the best part of the whole entrance hall. I already replaced one vertical post in the shorter right wall. And the lower front horizontal beam was party destroyed. So, there I installed a replacement part, leaving those parts which still are fine enough. But I decided to do it this way, as now I keep the roof all the time =)