Google Analytics - Cross Domain Tracking + troubleshooting

We run a website (based on typo3) and a webshop on different domains. ([login to view URL] and [login to view URL]). Traffic that is going from the website to the webshop and back is registered as a bounce in Analytics due to the different domains. Therefore, we need help with setting up cross domain tracking in Google Analytics. Apply only if you have specific experience with these type of tasks in GA. Please provide references and make recommendations on how to solve this. Also let me know what kind of access you require. Is there the need to do something in the CMS of the website/webshop for this cross domain tracking despite having the tags running over the Google Tag Manager? I would recommend the following approach: Day 1. Skype meeting to introduce project scope in detail (website and webshop) --> fix appointment for the next day for implementation. Day 2. Access to GA is provided via Teamviewer (tbd) and the implementation is done in a live session. Afterwards the system is tested with the Google Tag Assistant to make sure that all changes have the desired outcome. After this is completed, we would appreciate some advise on setting goals in GA - max. 1 hour. This approach is a suggestion - if you have a better one, feel free to mention it.