Since I recently faced the same challenge of importing a survey created with Limesurvey v 5.x into an older 3.x version, I am sharing my solution:

1. Export the survey at LS 5.x as tab separated value format
2. Open the TXT file with a text editor
3. Remove these two rows:
   1. ipanonymize
   2. tokenencryptionoptions
4. Save as TXT file
5. Import at LS 3.x

Depending on your survey structure and complexity, there could be further challenges to solve.
For me this worked for a multilingual survey with ~80 questions.

Let me add an initial step #0: Make sure that at any survey setting at LS 5.x you do NOT use "inherit" as setting. Instead, set a certain setting for every such value.

@Mazi: Sprachdisziplin bitte! Im deutschen Forum nur deutsch...