The stuff isn't easy. That's why it pays well, and it's a sought after profession.
Eventually, you'll find the classes get easier because you'll be more interested in the material.
You're starting off on the right foot. Get yourself affiliated with classmates (smart ones) and use study partners. Take advantage of your instructors' office hours if you need to. Most are more than willing to help. Just don't waste their time with BS questions. Have a purpose... get in, ask, get out. Show interest, but don't kiss ***. Make them recognize your name and your face. They'll remember you when they're grading your test.
Some courses are just harder than others, while some teachers are much tougher. You'll be met with the typical jerk-offs who will tell you "oh, I didn't study". Liars. And if they didn't, their GPA likely shows it. I knew guys who could float by and get a 2.5 GPA but I can count on one hand the people I went to college with who "just got it" and seemingly never studied and rocked above a 3.5. Fact is, most people just "don't get it". At least not right away. Study, practice, study. Try to find real world examples.
I graduated in May 2008 with a BS in Aerospace Engineering and a 3.33 final GPA. I didn't really start studying until my junior year and from that point I made only 2 B's in my last 4 semesters. It's not so much that I studied more. It's that I was actually more interested in the courses at that point. I hated statics/dynamics/mechanics. When I got into airbreathing/propulsion/flight dynamics, my grades shot up and my desire to learn increased.
If you have any questions, I'll try to help you. The best advice I can give you is to keep on truckin', man. Keep your head up, study hard, work hard, and you'll pull through. Don't listen to the dickheads who tell you it should be easy. It's not. Simple as that. My two good friends graduated at the top of our class and they worked their *** off to get there.