I attach a picture where someone told me there are problems in some measures with the Imaginary Bar Line. What can be fixed in this example?
By "imaginary bar line," I assume your colleague refers to the practice of notation wherein large beats are clearly defined. This will be best explained by a re-notated example:
Above, notice how every single large beat (1, 2, 3, and 4) is clearly shown and not hidden in the middle of another pitch. This allows the performer (especially those sight reading) to clearly see how all of these subdivisions relate to beats 1, 2, 3, and 4.
Contrast this with your example:
Here it's not immediately clear to the performer where beat 2 is. Is it where the right hand plays that C? And where is beat 3? (It's hidden in the middle of that dotted-quarter C.) Beat 4 is thankfully clear in the right hand, but it's only made clear after a potential confusion on that next-to-last A.
In a perfect world, it's best to show all main beats in the music; in 4/4 time, this would mean showing beats 1, 2, 3, and 4. This isn't always possible, so you at least want to show beats 1 and 3.