Dear Sebastian,
Yes, there is a way to restrict the memory quotas for each type of memory. If you go to transaction ST02 --> Menu --> Current Local Data --> SAP Memory --> Quotas you can see the limit for each of the types of memory on that instance. Also, in Current Parameters you can check each parameter with it value.
The Wait Time is the time that an unprocessed dialog task waits in the dispatcher queue for a free work process. Usually a High Wait Time indicates that there is not enough Dialog Work Process configured on the instance or that the work process configured are not able to finish with the process before there is another waiting to use it.
How many dialog work process do you have configured? You can use transaction /SDF/MON to monitor how many dialog work process the system have on a period of time. The transaction takes a snapshot of the system each interval and you can use that information to check if you have a problem with the number of dialog process, CPU, etc.
Please take a look to this URL for more information about transaction /SDF/MON:
How To Run /SDF/MON To Collect Snap-Shots
Best regards.