Hi TamaraS,
After I installed the 13.0.2 update on my mac Premiere Pro CC became unusable and eventually unresponsive.
If you updated your project file from the previous version, it might have issues. Create a new project, then import the problematic project into the new one. Same issue?
Another troubleshooting step to try is to repair Adobe folder permissions. It won't harm, only help. Premiere Pro CC, CC 2014, or 2014.1 freezing on startup or crashing while working (Mac OS X 10.9, and later)
Let us know if either of these things help. The tech is correct in stating that your system would work a lot better with 4K if you had more RAM and overall computer power, however, you should have acceptable performance with lower resolutions or even better, proxies. The recommended system requirements have been published for 4K here. Adobe Premiere Pro CC System Requirements
Thanks,
Kevin