Baseball Training Exercises

I live in the Netherlands and I play baseball in a lower amateur league. I’m 17 years old but since I’m still in high school and living in the east where there are way fewer baseball teams i’m stuck here playing a bit lower. The problem is that the pitchers here tend to throw real slow and by slow i mean in the 60-70mph range and it seems that i adjust my swing on the slow pitches, which means i swing slower and hit the ball less hard. Also, i’m not stepping forward to the pitch. I do this while in BP but in the game i just don’t. Can anyone give me some tips how to fix my swing and give me some exercises to train it with.

Thanks.