I am not sure there is an answer to why we use at instead of of that is substantially better than "Because that is the way English is." I am sure your native language also has cases where you use one preposition and not another.
But we often use at to mean "caused by" in the case of reactions, or to mean "on the occasion of".
"At my training" is fine.
Training is a noun, and like many nouns for activities (such as the names of sports) it is very flexible and can refer to a single session, a place you go to for the activity, or an activity you attend regularly. For example, "I'm going to football" could mean you are going to the place you regularly go to play ...
When you say "Change the quantity of an order", it means to change the quantity of the idea of the order.
When you say "Change the quantity on an order", it would usually mean that the order is a physical object, such as a piece of paper with an order written on it.
It's the same thing for changing the date. Using "of" instead ...
First, let's look at the sample sentences:
Which climate you live in? [Statement: I live in a tropical climate]
There is nothing to be scared of. [She is scared of snakes.]
I have something to talk about. [She talks about her brother all the time.]
I wonder who this book was written by. [The book was written by her friend].
If you have an action verb plus ...
If the firework festival was being held on a barge moored on the river you would say on the river. If it is being held on a piece of land next to the river you would say by the river or beside the river. If you say at the river people would understand you of course but it is not the most common preposition for an event y the river.
"by the river" would be apt.
"by some place" suggests next to, near or beside a place.So by the river would be a better choice
"at the river".Well, I have noticed "at" being used with river in few cases but as per my limited knowledge, "at" is generally used for specific locations or points in space.Since ...
File (noun) with means that you have entered something as a legal document in charge of ABC.
2. To enter (a legal document) as an official record.
In the charge or keeping of: left the cat with the neighbors.
Yes, it is correct to use with, although you could say that they looked at you in a contemptuous manner.
In contempt is a legal expression, used when some person/organisation is said to be in contempt of court.
It is also the name of a TV show.
English requires extra work for specifically pinpointing time ranges and time spans. You cannot merely rely on the prepositions. You will need to be certain and possibly confirm that the listener understands when. Your question overlaps with English speakers use of This Wednesday, Last Wednesday, Next Wednesday. These things can be understood differently ...