I presume that 2017 is the latest version that is now simply called "Audio Cleaning Lab" with no date. I expect that the time stretching feature is not included since Magix split the program into two, ACL and AML Premium. You will find all of the features in AML and I strongly suggest that you contact Magix and switch/upgrade to AML Premium. ACL is a stripped down version and what I consider to be a downgrade from the older versions.
Here is the Effects menu with Resampline/Time stretching at the bottom and the Time stretching screen superimposed that is in AML.