Incorrect file associations could be the result of underlying issues within your PC system. As such it is highly recommended to scan your PC for invalid registry entries, unused processes and other unfavourable system settings to identify slowdown issues.
The MGMF file type is primarily associated with 'MindGenius' by MindGenius Ltd..
A mind map is a diagram used to represent words, ideas, tasks, or other items linked to and arranged radially around a central key word or idea.
Mind maps are used to generate, visualize, structure, and classify ideas, and as an aid in study, organization, problem solving, decision making, and writing.