I'm a bit intimidated by this being my first critique but I'll try my best to give a just and fair review.
So first of all you described Richard and Till's love making wonderfully But it wasn't just straight forward they jump into bed and have sex. You once again brought in realistic concerns such as the lack of condoms and Richard's worry of having been too rough too fast with Till.
The sexy feel is broken by Till laughing at them having sex to their songs, but you do slowly regain the feeling as you go on.
The scene where Richard and Till are lying in the bath together was heart warming and tender. It was sweet the way they snuggled together, and quite adorable when Richard looks and sees that Till has fallen asleep. I must say this is my favorite scene of the whole chapter.
It was made all the better when Till asked Richard to marry him. I like that you didn't give the question a whole bunch of pomp to Till's asking but still managed to make it just as meaningful as it should be. I will admit a marriage proposal in the bathtub is a new one
The ending was wonderful! The perfect open-ended closing of the Silenceverse. You leave it open for others to add on to it, but also give it a marked ending.
I will say the only noticeable thing about the fanfic that I wasn't big on was the way Rachel and Till spoke to one another, though that's just me being picky. They are strangers and so will be formal, but to me Till and Rachel's language borders on being too flowery.
The area in which I saw this is when Till was talking about Richard and Rachel speaking about her dogs. Till can get away with this a little more than Rachel, because he's spoken close or like this throughout the fanfic, while Rachel is a quick character and it just doesn't seem to fit the way she would actually speak.
But other then that little thing I enjoyed this gorgeous fanfic, and universe you've created. I look forward to seeing more worlds and fan fictions from you