It is said that learning about fiqh and learning about the rulings of our marja is wajib. I have difficulties on understanding what I have read and learning in general and that means learning my fiqh has been hard, and I feel hopeless because my amal is fruitless. Can you please give me some advice

I recommend you read a simplified book of rulings. You may read this book:

If you read it you will know the main rules you need to be aware of.