Translate into German — the point is the relative pronoun.
Translate each sentence into German, using the German words given after the dash. Only the relative pronoun is checked — with its preposition, straight after the comma (…, mit denen …) — so keep that comma. The model is shown afterwards to compare the rest.
English often drops 'who' or leaves the preposition at the end: 'the friend I helped', 'the child I gave it to'. German always needs the pronoun, and the verb decides the case.
The landlord I transfer the rent to lives in Spain. — der Vermieter · die Miete · überweisen
The neighbour I help with carrying is 80. — die Nachbarin · helfen + Dativ · beim Tragen
The neighbours the garden belongs to are very nice. — die Nachbarn · der Garten · gehören + Dativ
The girl I showed the way to was from Italy. — das Mädchen · der Weg · zeigen
Tourists who like the city stay longer. — die Touristen · gefallen + Dativ
The man who owns the café is very friendly. — der Mann · das Café · gehören + Dativ
'The flat I live in' → die Wohnung, in der ich wohne. The preposition moves to the front of the clause.
The flat I live in is small. — die Wohnung
The house we park in front of is very old. — das Haus · parken vor
The neighbours we have barbecues with are from Poland. — die Nachbarn · grillen mit
The park I jog in is huge. — der Park · joggen
The street we live on is noisy. — die Straße · wohnen an
The shops I shop in are all nearby. — die Läden · einkaufen · in der Nähe
'whose' → dessen (masculine, neuter) or deren (feminine, plural).
The house whose roof is broken is being renovated. — das Haus · das Dach
The flat whose rent is so high is still nice. — die Wohnung · die Miete
The neighbour whose dog is always barking is nice. — der Nachbar · der Hund
The tenants whose flats are being renovated are living in a hotel. — die Mieter · die Wohnungen
The town whose centre is very old has lots of tourists. — die Stadt · das Zentrum
The houses whose windows face south are bright. — die Häuser · die Fenster · nach Süden gehen
All the cases mixed. Work out what the pronoun does in its own clause before you write it.
The house I live in is old. — das Haus
The house in whose cellar our bikes are kept is old. — der Keller · die Räder · stehen
The flat we're moving into is big. — die Wohnung · ziehen in (wohin?)
The tenants who were given notice are angry. — die Mieter · kündigen + Dativ
The landlord who never answers is difficult. — der Vermieter
The man whose house we're renting doesn't live here. — der Mann · das Haus · mieten