Aigel.
Thanks for welcoming me in. This is great motivation for me and I will update regularly.
The problem is the 53' in a 10k were under optimum conditions and in a downhill course (start and finish located in different points). My best time in a level 10k (loop) is around 55'. Also those are hal marathon times are attainable if I train properly, which is the big question now
Additionally I am now having some problems with my running since I upgraded my shoes to modern ones. I have been diagnosed as an overpronator but my stability shoes still cause me pain in the calf area. Next step is trying some compression socks in that area.