Hello guys I'm fairly new to cycling. I bought my first road bike 2 months ago and now im hooked. Eversince I bought the bike Ive been riding 1 or 2 100km ride weekly depending on my work schedule but usually sundays, on the weekdays I do 20-35km rides. I really want to be faster, it frustrates me that I couldnt barely hold 40km/h and couldnt reach 50km/h. Can you guys give me tips on what gears to use to maintain 40km/h or even reach 50km/h? Training tips are also appreciated.

I originally bought the bike to lose some weight from172cm 80kg to 74kg now. I wonder if my weight is also a limiting factor on how fast I could go on my bike?

Sometimes Im really pedalling so hard but still couldnt reach 40km/h. I really want to know whats going on. Is it that hard to reach 40km/h on a bike? How are people doing it?