thanks for your answer. 
i think now i understood how to save a list to the db. with one list, everything works great, (including foreign keys)
but now everytime i try to add another list to any other entity class i get an ivy:error:persistence, with following error message:
    IvyScriptRuntimeException: IvyScript Runtime Exception in
    	Instruction:
    		ivy.persistence.axsosUnit.findAll(teamprojekt.Job.class)
    	Block:
    		teamprojekt.showDashboard.showDashboardData out;
    		out = in;
    		in.data.closedJobs = ivy.persistence.axsosUnit.findAll(teamprojekt.Job.class);
    
    IvyScriptMethodInvocationException: Error calling method findAll(java.lang.Class) on an object of class ch.ivyteam.ivy.process.data.persistence.internal.IvyEntityManager.
    
    PersistenceUnitException: Failed to excecute operation "findAll" for persistence unit "axsosUnit".
    
    PersistenceUnitException: Could not create EntityManagerFactory of persistence unit'axsosUnit'
    
    PersistenceException: [PersistenceUnit: axsosUnit] Unable to build EntityManagerFactory
    
    MultipleBagFetchException: cannot simultaneously fetch multiple bags
I have read, that you cant use two lists in the same entity class, but i use them in different entity classes. maybe because they are nested?
the structure is: 
institutionList is inside education which is inside application which has the other list.
I have also read, the solution is to use a set instead of a list. can you explain how to do this?
I've tried to change the list to  a set from the entity class wizzard, but without success.
can you show me how to do this?
thank you very much