Running

Having changed my training to an aerobic one, I’ve changed my nutrition as well. I cut out some refined carbohydrates, drink no more fruit juices, nor eat sweets, chips, soda, or cakes. This is to change my body metabolism to burn fat instead of glycogen. I have always had a sweet tooth, so eliminating sweets was most difficult for me. Moreover, the New Year's celebration, with all the sweet stuff, is coming up.

The second week was pretty good. I ran 12 km on Tuesday and Thursday. It was rather boring to run in the park where a lap is only around 1.5 km. I ran a short distance on Saturday, and after that I went to the swimming pool with my wife. My Sunday run was great. It started getting colder; I think -2 or -3C. The puddles began freezing. I ran one long loop instead of a couple of short ones. I ran 22 km pretty easily. Perhaps, my nutrition change worked. Haha, just kidding.

The third week turned out to be hard. The weather got worse. It was -10C in the evenings, without snow. There were only cold and dust in the town; it was the worst example of the weather for me. I could hardly make myself go for a run. Nevertheless, I made my weekly mileage. I added some hills to my Sunday run. The elevation was around 300 m. As a result, I ended that week with 61 km “in my bag”.

Very well written.  Although there were some mistakes, your post "by and large" (= for the most part) was written in an English that sounds authentic and natural.

On Saturday and Sunday, I did 50 km. each day.  Of course, I was in my car!