I notice you're asking for a "full story" related to (a version released around 2014). However, your request is quite open-ended.
: A revamped interface with new workspace options designed to mimic Adobe Illustrator or Photoshop, making it easier for users transitioning from other software. Corel X7 Version
Go to Tools > Options > Global > Memory . Increase the RAM limit to 50% of your system RAM. Also, ensure you are running the 64-bit version of X7 (not the 32-bit one accidentally installed). I notice you're asking for a "full story"