But what if I created the the comp earlier first with AE and want to put it dynamically on the timeline in premiere for further dynamic changes able, how to proceed?
In Premiere: File > Adobe Dynamic Link > Import After Effects Composition. Then, in the dialog that appears, navigate to your AE project, select it, and then pick the comp or comps you want.
Even easier: drag your AE comp from the AE Project Panel and drop it in Premiere's Project Panel.
If I have saved the project with save as with an new name and then change titles in one of them, will the changes take affect also in the other one? Or if i need to import titles from the other project, can it be done?
Titles are saved into the project file, so by duplicating the project/saving it to a new file, you're effectively creating new titles. When you change a title in Version A of the project, Version B's titles won't change.
And: I also need to do minor changes in theese AE projects inside Pre projects since they are titles to the movies in different languages
In this case, you'll either need to create duplicates of your comps in your AE project, and replace the original comps in the duplicate Premiere project, or duplicate the AE project and change the comps there, then replace the DL comps in your duplicate Premiere project. Note that if you do the latter, be sure to save your AE project file with a distinctly different name--don't use serial numbers, e.g. Project 1, Project 2, etc. This can cause some issues with Dynamic Link. However, if you do something like Project English, Project French, Project Spanish, you'll be fine.
Thank you very much!