Open the console by going to the views menu, then select console, after it opens, place the cursor just above the top edge of the console and it will change shape into a resize/drag tool, now drag the console up to resize it. The console can be closed by clicking on the double arrow icon located on the right side of the bottom edge, this will allow full view of the track view again.
 
With the console open, click on the Bus tab and then click on "insert stereo bus" to create each new stereo bus. (There is an 8 bus limitation in Music Creator)
 
Name one bus "Voices", name one bus "Sound FX", these two busses are going to be used as subgroups.
 
Name your other busses such as "Reverb/Cave" or just "Cave" and so on, these busses are going to be used as aux busses.
 
Use the output assign box located in the In/Out module near the bottom of each channel to assign them to the correct subgroup, (actor's channels to "Voices" and sound effects channels to "Sound FX", if you have a narrator track, you might want to leave it assigned directly to the master bus so that it will not have any location reverb applied to it.
 
On each of the two subgroups go to the Sends section and click the + icon to create a send to each of the aux busses, after creating each aux send, you will need to manually turn that send off until you are ready to start setting levels and adjusting effects settings, otherwise all of the sends created would be turned on at the same time, and you don't want that!

Ok,got it so far (i think)... but how do i send the voices and the sound fx (bus) at the right "time/section" thru the -for example-  "cave bus" . Is there also an automation function for it like on panning and volume? At least i couldn`t find anything like it. But it would make sence to me...and by the way - Thank you!

You're welcome!
 
There are a couple of ways to do it,
 
Automation
First is by using track envelopes to automate the send levels on your voices and sound effects bus tracks, this is really the main reason to use the subgroup buses, so instead of needing to automate 6 or 8 or 20 individual sends to the cave aux bus, all of your tracks are now gathered into just two subgroup buses, now, by automating the sends on just those two buses you can get everyone into the cave at once. I don't know if the volume and panning automation you mentioned was done by clip envelopes or track envelopes, but to automate the sends on buses you're gonna need to use track envelopes.
 
 
Manual
The second way would be to mixdown each scene separately and making manual adjustments to the send levels before each scene mix, then when that's done, import all of those scene mixes into a new session, layout the scene mixes in the right order, and then do one more final mixdown to make the finished mix.
 
 

...and once again i have to ask you how exactly to do that ( the first way -automation) ?

https://www.cakewalk.com/Documentation?product=Music%20Creator%207&language=3&help=Tutorial7.4.html
 

thanks for that... but is there a different way to do it like just drawing a curve like it can be done with the paning and volume automation?

One of the controls that can be automated is the "MUTE" button.  Mute when the actors are "outside the cave" then unmute when the actors go into the cave.

At this point you should have all of your tracks routed out to one of two buses, either Voices or Sound FX, this routing should be done using the In/Out controls, each of these two buses should have sends on them for each of your scene effects buses, all of these sends should be set to post-fader and turned down to -INF.

Using the little double arrow icons located on the border of each view element, collapse all of the open views, (the inspector, the browser, and the console which should be in the multi-dock) so that only the track view is open, it will now be the main work area for this automation.

In the track view, on the bottom border under the track controls there is a button that opens and closes the bus pane, this needs to be set to view the bus pane, then grab the horizontal divider and drag it up until the bus pane is taking up most of the view.

Double click in an empty area of the track controls area on the voices bus and it will expand to take up the whole visible area of the bus pane.

On the top of the track view there are two buttons, standard and advanced, select the advanced button and all of the controls will become visible.

On the voices track controls there is a button that says "None", that is the automation envelope edit filter, click on it, and in the automation menu there will be one that says Cave Send Level, clicking on that will make the envelope for automating that send level visible, you can now add nodes and write your automation.
 
Place the cursor on the timeline where you want the "cave" effect to start, and create 2 nodes about 1 second apart, then grab the node to the right and drag it up until the send level is where you want it, at the end of the scene, create 2 more nodes and drag the one to the right down to -INF to shut off the cave effect.

Strryder,
 
Your posts in response to the OPs questions have been extremely helpful.  I've learned a lot from reading your responses.  It is very easy to visualize the steps from the way you present them.  THANKS!

Im already working on the project and doing fine so far because of all the useful advices.Some VST`s don`t work properly ,but that`s another story for another thread, i guess.  Thx to everybody who tried to help me with my issue.