Sharepoint Online

We are looking for an expert in Microsoft Sharepoint Online to help create a system to manage and track client files and data between our team members. The project will be two different sub systems - 1. A marketing/call log system to keep track of potential clients with ability to schedule follow up calls on a shared calendar. 2. A client file management system to keep track of client details and what stage the file has progressed with scheduled follow ups on a shared calendar. Both of these systems have been started in our Sharepoint portal but we need additional assistance for interface customisations.