The conversation moves so fast!
For shampoo and such like when traveling what I've been doing is this: shortly before traveling, whenever a bottle currently in use looks like it is about to end, I put it aside unfinished and open a new bottle. The new bottle keeps getting used at home, the mostly-finished bottle gets taken with, (topped up from the new bottle before leaving if necessary). The plan is to use it up completely while away, and toss the empty bottle. It takes a little practice to get the amount right, but seem to have it sorted now. Works with toothpaste, also.
And I actually keep aside socks and knickers that are almost too far gone to wear specially to take on holiday. Particularly appreciated on the last couple of days of holiday when there is no chance to wash clothes and get them dry in time, as I can wear and then toss. Also means not so much of that huge pile of washing that, I at least, used to always end up with when just back from holidays.
And also pack zip-lock bags with washing powder and spices (not in the same bag!) as we usually self cater, and shops tend to sell these in quantities way bigger than one needs for that amount of time. The amount left over at the end of the holiday is usually none, or small enough to not feel guilty about tossing.
Maybe that sounds over the top, but I'm the one that has to do all the lifting of luggage (DH has back problems), so anything that minimises weight and effort is appreciated.
On shoes by the door. We used to have one of those Ikea shoe racks, but the bits where it folds out broke, and Ikea won't sell replacements to that section, but told us we should just buy a brand-new shoe rack (so the same bits can break all over again!?).
So then I copied something I saw one of my neighbours do: tiny bookcase just by the door - ours is a cheap and small one from Ikea. Forgot the name, but think Billy style, but not quite as high or as wide. For three of us, all shoes, for all seasons, fit on (it's a tight squeeze!), and as soon as they no longer fit, I know we have to weed some out. Keys and folding umbrellas get placed on the very top shelf. Then attach a curtain rod level with the topmost shelf, and use a nice bit of cloth as a curtain so that you don't actually have to look at all the shoes there, but can draw it aside when you do need to get at them.
Wannabe I'm impressed that you want to learn Japanese. It's a lot of work! Where in Germany are you?