Then I go to gtmetrix or pingdom and compare my site posts with another one from another theme, just to compare the speed, and both sites score similarly.
Besides pingdom is telling me that my post load is from 2ish, 3ish, 7ish seconds depending on location. But as I said when I load any blog post it takes like 15 seconds to see the column, at least for me.
Do you know of any similar issue with the GP themes from other people?. I wonder if this is a GP issue or might be something else
both the sites you linked load in under 2-3 seconds for me, i am based in the UK.
It sounds more like an issue with your local machine or service provider.
Any delays on loading the adverts is not GP related.
If you want to look at speed improvements then this guide can help: