Adding a break is totally possible. To do it, you can create an extra event and add a conditional route there, which originates in the last event in your trial sequence. Since you want to stop every 2 blocks of 25 trials, you can use both the block and 'in-block' trial numbers to define the 'break' condition for the created conditional route. For example, this would stop the sequence on trial 50th, 100th, 150th (and so on) trials:
((TrialNumber==25) && ((BlockNumber%2)==0))
If you use a total trial counter, the 'break' condition is simple:
((TotalTrialNumber % 50) ==0 )
Once the break event is entered, you need to build up the 'return-and-continue' logic. Normally, you would ask a participant to press a button to continue. As the simplest example- create a new conditional route, from the break event to the first event in the trial sequence and define the route condition with 'Is Triggered' property of the Button element.
You can also check the demo experiments included in EventIDE. Many of them have a break event and you can how it's implemented in details (see, for example, the 'Visual Simon Task').