"That is the house that I bought."
Translation:Das ist das Haus, das ich gekauft habe.
Ich danke Duo ist nicht richtig. "Das is das Haus, das ich gekauft habe," ist "That is the house that I HAVE bought." Es ist nicht "That is the house that I... bought." Die erste ist "past tense," und die letzten "past participle tense" oder "past perfect tense" ist. (Sondern ich bin kein Lehrer von Englisch grammar oder Deutsch.) Ich hoffe dass hilft :)
Sorry, guys, but no. German native speaker here and my mom is a German teacher who always lectured me...
In German, these past tenses work completely different than in English!
The simplest way to discern them is probably that one is used more in a casual setting and one in a more formal one.
If stories are told or written in books, they are usually written in Präteritum (what you referred to as simple past): "... und sie lebten glücklich bis an das Ende ihrer Tage." - "...and they lived happily ever after." If you write a dissertation or hold a speech in front of the senate you hopefully use Präteritum because Perfekt would be unprofessional.
You use Perfekt (which you referred to as past perfect), however, almost every time you open your mouth in conversation or write an email. If you start with Präteritum in an everyday setting, they will look at you strangely.
From context we can conclude that this is supposed to be direct conversation and it would be highly unusual to use Präteritum in this case.
Remember: in conversation, use Perfekt (past perfect); in books, use Präteritum (simple past)