All applied differential equations are solved via the following steps:
1. Understand what the question is asking.
2. Convert the request into mathematical notation.
3. Solve the differential equation(s).
4. Interpret the solution.
If you are having difficulty solving applied differential equations, figure out which step is causing the problem. After finding the weakness, use the following to improve:
1. This is likely a difficulty in conceptualization. You may be able to solve equations which are already set up for you via rote memorization and intuition, but without an understanding of what you are doing. Return to the basic concepts to understand what is being done. What are derivatives? What is differentiation? Can you explain what is happening out loud?
2. The saddest mathematical difficulty is when someone is limited by their arithmetic, as it will slow them down in every moment despite being so easy to master. The second saddest difficulty is in notation. If you cannot read notation out loud, then you do not know it.
3. This is lack of practice. Find and complete practice problems until you have an intuitive, well-oiled understanding of solving derivatives and differential equations. If you understand the problem, can convert it into notation, and then get stuck trying to solve it, you need practice.
4. If your problem is #4, then it is really #1. An inability to interpret the solutions means you do not know what you have solved.
If you do not know what your weakness is, try to teach. The great benchmark of understanding is the ability to transfer it to others. If you can teach a concept, then you know it. If you cannot, then you don't.
It is great to teach a classmate or a friend, but that is not required. You can teach your rubber duck or your wall. It will still be helpful.
I am suggesting that studying with someone worse off than you can be more helpful than studying with someone better off than you, on the condition that they are able to focus and are interested in learning the material. As a bonus, you get to help someone!