My spanish tree has changed: under the title/Heading looks like it's written in arabic
You can send a bug report to Duolingo's staff
Another discussion about the same issue
I've seen several of these reports. You can edit your post and change the topic to "Troubleshooting" and as Pentaan mentioned you can open a bug report: https://support.duolingo.com/hc/en-us/articles/204728264-How-do-I-report-a-bug-
I don't know of a fix, but that's the best way to get help from staff.