"When do I take my horse for a walk?"
Translation:Quand est-ce que je promène mon cheval ?
I agree that this is tricky because it really needs to be explained.
When you want to use the most formal interrogation form with the inversion of Verb-Subject pronoun, you may be faced with combinations of sounds that are not easy to pronounce. So, the French language has managed to correct these sound conflicts with various additions or changes:
- comment vas-tu ? -> no problem
comment va-t-il ? -> conflict a-i solved with the addition of a T between hyphens.
il mange -> no problem
mange-t-il -> same solution as above.
je mange -> no problem
mangé-je -> sounds ge-je don't work well, so an acute accent is added: manGEH-JE
je me promène -> no problem
- me promené-je -> sounds me-ne-je don't work well at all, so same as above + deletion of the grave accent: proMEU-NEH-JE
Fortunately, for the last two examples, there are other solutions to ask the same questions: "est-ce que je mange ?"; "est-ce que je me promène ?"
Verbs have to be conjugated: prendre is the infinitive (non conjugated) form. So "je prends".
"promène" is 1st or 3rd person singular indicative present of verb "promener".
"a walk " is not a verb, it is a noun = une promenade
So a more literal translation is: "Quand est-ce que j'emmène mon cheval en promenade"