1. "Does a company need a device like a cisco switch meraki to get access to the cisco system manager MDM or can i only buy the SM license and get access to MDM to register mobile phones from members? " There's no requirement for any Cisco hardware to use Systems Manager. It can be used completely in isolation
2. "The Documentation from cisco says, after the installationa a EMM network should be created and all the networkdevices from the company should be added..... so its that easy ? after adding the devices the network is integrated in the meraki cloud?" There are several enrollment options available to you: Where your company owns the device, you can use things like Apple's ADE ( https://support.apple.com/en-us/HT204142 and https://documentation.meraki.com/SM/Device_Enrollment/Apple_Automated_Device_Enrollment_(ADE) ) or Android Zero Touch (https://documentation.meraki.com/SM/Device_Enrollment/Android_Zero-Touch_Enrollment ) . Where you are considering BYOD (where the end user owns the device, then the user can enrol using the Systems Manager enrollment portal ( https://documentation.meraki.com/SM/Device_Enrollment/Enrollment_and_Self-Service_Portals_for_System... )
3. "What is the license cost when we have like 200 members in the sportsclub and everyone brings around 2 devices so around 400 devices." If you reach out to your local Meraki Partner, they will be able to provide a quote for you
4. "Whats the big difference to other software like microsoft intune?" Simplicity with Power. Secondly, there's lots of synergy with other Meraki capabilities as well as Cisco products
I hope that helps!