okay let's begin: (be prepared, some of them might sound really strange

"Nicht das gelbe vom Ei."
(Not the yellow of the egg.)
Meaning: Not the best.
"Durch die rosa Brille schauen"
(looking through rose colored glasses)
Meaning:,having an optimistic outlook, seeing only the good side (can also mean that somebody has fallen for someone that hardly, that the Person overlooks every flaw of their crush.)
"Klappe zu, Affe tot."
(clack closed, monkey dead)
Meaning: you can say this when you close a clack or finish something. it's like "alright, I'm finished." "Affe tot" (monkey dead) is a metaphor for "work is finished". So when you are moving and brought the last few things out of the old house/flat/whatever and close the door for the last time you can say this.
"Sitzt, wackelt und hat Luft."
(Sits, wiggles and has air.)
Meaning: something fits (like a picture on a wall or a book in a shelf)
"Alter schützt vor Liebe nicht, Liebe aber vor dem Altern."
(Age doesn't protect you from love, but love does from aging.)
Meaning: Even if you're very old, you can still fall in love. But if you fall in love, it makes you feel younger.
"Abwarten und Tee trinken."
(Waiting and drinking tea.)
Meaning: Just wait what happens.
"Sitzfleisch"
(sit meat)
Meaning: it's what you sit on-your bottom.
"Kuddelmuddel"
(???)
Meaning: Kuddelmuddel describes an unstructured mess, chaos, or hodgepodge.
"Das macht den Kohl auch nicht mehr fett."
(That doesn't make the cabbage fat anymore.)
Meaning: That little detail doesn't matter anymore, compared to what happened.
"Auf biegen und brechen"
(On bending and breaking)
Meaning: At any cost.
"Mit jemandem Pferde stehlen können."
(To be able to steal horses with somebody.)
Meaning: You can have a lot of fun with this person and be crazy together.
"Eselsbrücke"
(Donkey bridge)
Meaning: A trick to remember something better.
"Weichei"
(Soft egg)
Meaning: someone who is weak and cowardly.
"Kummerspeck"
(Grief bacon)
Meaning: the excess weight put on by emotional overeating.
"Ohrwurm"
(Ear worm)
Meaning: When a song gets stuck in your head, you have an "Ohrwurm" of this song.
"Ach du grüne neune!"
(Oh you green nine!)
Meaning: Awkward surprise.
"0815 (null acht fünfzehn)"
(zero eight fifteen)
Meaning: Totally ordinary.
"Man soll den Tag nicht vor dem Abend loben."
(One should not praise the day before the dawn.)
Meaning: Don't be happy about something too early-it could still get worse.
"Jacke wie Hose."
(jacket like trousers.)
Meaning: whatever, i don't care about that little difference.
"Wie mann es in den Wald ruft, so schallt es wieder raus."
(Like one calls into the forrest, it resounds the same.)
Meaning: You will be treated just like you treat others.
"Stille Wasser sind tief."
(Still waters run deep.)
Meaning: The kind ones may be worse than you expect.
"Alle Wege führen nach Rom."
(All paths lead to Rome.)
Meaning: There's more than one way to reach your dream/goal.
Enjoy!

~ Vampi ^vv^
P.S.: If you know some more german sayings or find mistakes in this list, don't hesitate to PM me

I also want to thank everybody who helps ans helped me expanding and improving this list!