I have a landing page "non-open" to the public with google tag manager and analytics implemented ( https://themowe.com/ ). And I obiously want to track visitors and his actions etc with Google Analytics and Google Tag.
I am pretty sure I have introduced the codes as Google advices, but when it comes to check the instalation with the Tag Assitant it gives me 4 errors.
May be it is nothing because I see the same errors here in Stackoverflow, but I want to make sure the tracking is correct. Any expert in the room? Thanks
Ignore that. It's not a problem with your code, it's a problem with Google Tag Assistant.
Google Tag Manager introduced 7 character account numbers a while ago, however the Tag Assistant only recognizes the old six character format and flags newer account ids as errors.
Also Google changed the recommendations for GTM code integration recently - it is now fine to put the code in the head of the page, however the Tag Assistant still flags this as an error.
You still might have a problem, though - the Chrome Google Analytics Debugger extension shows two Google Analytics trackers (one with the current Universal Analytics, one with the legacy ga.js) that track to the same property. This will quite probably result in double tracking. You should remove the legacy version.
My Tag Assistant is showing 1 error on your site: "Invalid or missing account ID (GTM-PLVZ436)". Make sure that you copied the right snippet from GTM's dashboard and make sure that you have published at least the first version of GTM: https://support.google.com/tagmanager/answer/6107163?hl=en To me, it does look like you placed the snippets on the right places.
Also, try to enable Preview Mode on GTM and open the site on the same window (non-incognito). It will tell you which tags were fired, as well as the events that fired them. This is useful to see if the Google Analytics tracking code is getting fired on your page. If so, you should see yourself on the "Real Time" section on Google Analytics, provided you're not filtering out your own IP.