Your question is so general that I cannot answer it in specifically. However, i will give you the overview of business cycle which includes some phases with different struggles. In the early business stage when you just set up, you have to face with customers, how to have their attention due to your new products. You also prepare some first months to bare loss, human management. Everything is a mess at the beginning. After doing business for a long time enough, you have to face the development of products, increase profit, customer management, potential competitors and risks...Then, after development stage of product, you have to do a lot of efforts to make sure your revenue not decline. These struggles in this stage could be decreasing revenue, losing customer if you do not create the new products or make any improvements.
Every Business has different struggles at different stages, Initially the struggle is to survive and client acquisition while maintaining costs as you wont be earning enough or no profits, Once the business is established you will struggle with more executive decisions such as expansion strategy, staffing strategy etc.
The main struggles I find are around time management and prioritization. In my early career, I found that I would spend too much time on tasks that weren't part of my core goals and so would invite time pressure. I found that learning to prioritize and communicating clearly with my manager to understand his priorities was a huge help. I would also ensure that I allocated my time to my different project according to what priority level was assigned to it.