I think that value will fit your opening_hours tag:
opening_hours=Tu,Th 12:00-14:00; Su[2] 11:00-14:00; 17:00-19:00 "2 evenings per week (advertised locally)"
Here you can evaluation this setting (try to press -/+ 1 week buttons to test):
https://openingh.openstreetmap.de/evaluation_tool/?EXP=Tu%2CTh%2012%3A00-14%3A00%3B%20Su[2]%2011%3A00-14%3A00%3B%2017%3A00-19%3A00%20"2%20evenings%20per%20week%20(advertised%20locally)"&lat=54.4&lon=18.4&mode=0&DATE=1739382840000