As I mentioned,

When I use intend the finish date of the dependent task stops being dependent on the start date of the final task.

And it really doesn't matter whether the tasks get linked to another tasks when intended or they are just intended not getting linked to any task.

The same result I get when already well intended tasks get a change in the final task finish date (must finish on constraint). (Result--finish date of the dependent task stops being dependent on the start date of the final task).

And I can't remove "must finish on" constraint, because otherwise the program does whatever it wants with duration and finish date keeping start date unchanged. (regardless I change finish date/ duration)

The funny thing is that it is within this file only I am not sure what is wrong with this file, but it actually doesn't link start date of the final task to finish date of the previous task at all

When I did completely the same in a new file it all worked well (the finish date of previous task was dependent on the start date of the final task).

Btw there is no such problem with other tasks that are dependent on the "previous" task

I am totally new to project management software, so it is first software I work with.

I appreciate any help.