Can you imagine, I measured everything cell by cell, tried my best, and it still turned out so crooked...

Coordinates exist precisely for mirroring purposes; calculate them, set them, and check.

or at least, so that this task ("Kill 'em all") is displayed in Russian.

Method 1
You can open the map using an archiver.
Find the files
objective-desc-text.txt and
objective-caption-text.txt and write your own description.
Method 2
You can also do this in the object properties. Find the task – "Kill 'em all" should be in the primary settings, and 0 should be set there; change the desc and caption. But the second option needs to be explained in more detail for beginners.