I’ve done many walking lately and didn’t get any of the badge... why?
Do you see your walking activities in Garmin Connect and are they logged with activity type "Walking"?
You can see all your walking activities here:
Do you see at least 5 logged after the date 2020-04-28?
Hard to tell without seeing the direct links to the activities, but if all those ativities are just Move IQ auto-detected walks, then they probably do not include GPS data, or do you see a map with the track of the walk when you enter the Activity detailed screen? If not, then you may need to turn on the GPS Activity Tracking option in your FR235:
Or starting the walk as an Activity manually. If there is no walk activity profile on your watch, you can add one as a custom profile, or simply start it as Run, and then changing the type to Walk in Garmin Connect.