App video

Is there a video where I can see how an app works ?, What If I buy an app and it is not what I was looking for?  

Every app works differently so there is no general video but the following article:

https://akaunting.com/docs/user-manual/apps

You can also read their description to understand what they do. Also, you can ask the app developer if the app has the features not mentioned in the description.