Hello @karolinafotyga
Thank you for your inquiry and I am happy to assist you with this.
I’ve checked the Gtmetrix report and found the following:
There are 13 static components without a far-future expiration date.
https://fonts.googleapis.com/css?family=Roboto%3A700%2C400%2C300&ver=1589053167
https://fonts.googleapis.com/css?family=Roboto%3A100%2C100italic%2C200%2C200italic%2C300%2C300italic%2C400%2C400italic%2C500%2C500italic%2C600%2C600italic%2C700%2C700italic%2C800%2C800italic%2C900%2C900italic%7CRoboto+Slab%3A100%2C100italic%2C200%2C200italic%2C300%2C300italic%2C400%2C400italic%2C500%2C500italic%2C600%2C600italic%2C700%2C700italic%2C800%2C800italic%2C900%2C900italic&ver=5.4.1
https://www.googletagmanager.com/gtag/js?id=UA-15356433-7
https://fonts.googleapis.com/css?family=Open+Sans:400,400italic,700,700italic
https://fonts.googleapis.com/css?family=Roboto:400,400italic,700,700italic
https://track.mailerlite.com/webforms/o/1530178/s9h9k1?vee71a8848f3cc4af6b2730283dbdc659
https://www.google-analytics.com/analytics.js
https://connect.facebook.net/en_US/sdk.js
https://pixel.wp.com/g.gif?v=ext&j=1%3A8.5&blog=128112833&post=8957&tz=2&srv=www.karolinafotyga.com&host=www.karolinafotyga.com&ref=&fcp=2389&rand=0.7372875324001249
https://u.heatmap.it/conf/www.karolinafotyga.com.js
https://code.jquery.com/jquery-3.2.1.min.js
https://fonts.googleapis.com/css?family=Lato:400,400i,700,700i|Merriweather:400,400i,700,700i|Montserrat:400,400i,700,700i|Open+Sans:400,400i,700,700i|PT+Sans:400,400i,700,700i|Raleway:400,400i,700,700i|Roboto:400,400i,700,700i|Source+Sans+Pro:400,400i,700,700i
https://www.facebook.com/common/cavalry_endpoint.php?t_cstart=1589137998405&t_start=1589137998406&t_domcontent=1589137998540&t_layout=1589137998644&t_onload=1589137998644&t_paint=1589137998644&t_creport=1589137998644&t_tti=1589137998540&lid=6825295730897380832-0
As you can see these are all external resources and that being said, W3 Total Cache or any other plugin for that matter cannot handle those files because they are coming from the external server.
The potential solution is to host those files on your server.
Thank you!