first of all, let's analyze how many celery services you need.
the main thread is a must, so you need a thread main,
because group2 is executed after group1, so group1 and group2 should be Synchronize methods, executed in the same thread; and because they need to be asynchronous to the main thread, they should be executed in a celery.
so the final structure should be roughly as follows:

1. group1 corresponds to celery1, and executes
in celery1
2. group2 corresponds to celery2, and executes
in celery2
3. there is a celery3, group1 and group2 that Synchronize should execute in the celery, and group2 should execute
first.
4. celery3 executes on main thread

roughly implement:

@app.task()
def group1():
    return group([add.s(2, 2), add.s(4, 4),])
    
@app.task()
def group2():
    return group([add.s(2, 2), add.s(4, 4),])

@app.task()
def celery3():
    result = group1.delay()
    -sharp sync group1
    result.collect()
    group2.delay()

-sharp main thread
celery3.delay()