Tip: Choose a file structure that allows teams or team members to separate their work.
One strategy to avoid merge conflicts for specific ARXML files is to isolate pieces from the model into separate files. The collaboration environment and process should be analyzed to identify which parts of the model that often are edited by several people simultaneously and split those parts into several files. Thus, the risk of merge conflicts is reduced as the likelihood of several people making changes to the same file in parallel is lowered while still enabling co-workers to make any changes they need without involving designated modeling departments.
The content can be split based on a group of AUTOSAR Elements, whole AUTOSAR Elements or separate aspects within the same AUTOSAR Element. For example, if one team is responsible for designing the Service Interfaces of an application while another team sets up the diagnostics, splitting the application model into one file with Service Interface Ports and another containing Diagnostic Ports and Mappings could be considered.
Related Tool Features
Many model elements can be split into multiple files. In any comfort editor, the AUTOSAR Model Explorer or the DaVinci Project Explorer, open the context menu of a splitable element and click 
Split to File... to split the element to another file. For a practical instruction, refer to the Splitting AUTOSAR Elements Across Multiple Files cheat sheet.