For wall question:
1. Select the wall between two rooms;
2. Right click on selected wall;
3. Split wall;
4. Delete one section;
5. Resize the remaining section to Your desire length.

For room question You have two options:
1. Delete one room & resize manually the remain.(It's a little bit hard)
2. Delete both rooms & recreate automatically by double clicking inside the new walls area. (It's the easy one)