Grammatik

Grimm Grammar - explanations and exercises for many different grammar topics with themes from Grimm's fairy tales - https://coerll.utexas.edu/gg/index.html

Das doofe Fischlied (Adjective Endings) - https://www.youtube.com/watch?v=ZZs6OLcmt_M

Passive Voice - https://www.dartmouth.edu/~german/Grammatik/Passive/Passiv.html

Präpositionen

Genitive, Dative, and Accusative prepositions - https://deutsch.lingolia.com/de/grammatik/praepositionen/faelle

Video to help remember how to use two-way prepositions - https://www.youtube.com/watch/?v=VHqSHTpmXlA

Präteritum

Wise Guys "Nur für dich" song lyrics - https://wiseguys.de/songtexte/details/nur_fuer_dich/