Serve Scaled Images and data-vocabulary.org schema Error

When I am Checking my site https://learnforget.com/ on Gtmetrix https://gtmetrix.com/reports/learnforget.com/Rvf8ZZJU then it shows an error which is Theme doesn't offer to Serve Scaled Images, so can you plz solve this issue using CSS code? because of this issue impacts on site speed. I am also seeing data-vocabulary.org schema deprecated issue in Search console, as I know google stopped giving support to this schemea type now they only support schema.org. So can you plz remove this schema code from the theme?