so my requirement is this: A case should be automatically updated (status set to open) 5 days after the last modified date from the case (with some conditions). As an extra there should be an auto-task created which stated exactly this.
When I debug the flow with a case it looks good. When I activate the flow nothing shows up in the monitor. Even setting the time to 5 minutes (instead of 5 days) did nothing.
Sounds like you have legacy Cases that you want the flow to apply to.
Flows will only execute if a Save event occurs on the record. Legacy cases will not undergo save operations in most situations
To coerce legacy cases into the flow you have some options
Toggle those cases such that the flow entry conditions would be false and then toggle back so the entry condition is true. You could do this with Data Loader or anonymous Apex. It looks like you don;t have to go too far back in time
Add a new custom field on Case called Is_Coerced_Into_MyFlow__c (checkbox, default false)
Add that field as an OR condition to the Flow entry criteria
Use Data Loader or anonymous Apex to set the checkbox to true for the relevant records
Be sure to clear the field after all the coercions (either in the flow itself or via other means)
You could use a Schedule-triggered flow but this can only run once per day and would have to look back several days each time it ran. I'd avoid this route given that record-triggered flows with scheduled paths is the preferred solution for this use case
Coerce_to_Flow_X_entry_conditions__c(boolean) and use data loader to set to true on legacy cases