Thank you for your answers!

I understand it, you spared me a lot of money

Which saddle (brand, shape, etc) are you suggest to me? My legs are not tired after 40-50km but the sitting is not so comfortable (I use cloths).

And pls tell me about the differences between wheels and tires. What can I gain with a better wheels and tires? Originally I bought the bike with Bontrager R1 700x23c.

My main goal to is to keep 30km/h for a long distance. Therefore I train every day, I ride 42km. I have a good track/route. A little uphill for 20km than turn back.

I uploaded this track. I know I'm an amateur.