Mobile Application -- 2

I need an application that is tailored towards my business. I need the ability to- track sales, profit, Cost of goods. The ability for me and my team to track expenses, leads. Create tasks and assign to employees. Invoicing with the integration of quickbooks for payment. I am currently using an app, but I do not like the design and layout. It has the above features and application integration which is great, but I would like to make a new one that is similar, but more simple with few added features. By developing this app, It’s important we customize legally (no copying snippets of other codes) to avoid legal issues.