When a customer chooses a language version at first time, language version should stay with him during hole visit. But it does not work. Please lets try to buy something as s German. On every single page, You have over and over choose language again because language always goes to default language. Do You understand me?
Link to a page where the issue can be seen: hidden link
I just tested this on your site and I can see the issue happening.
Can you please try this:
First, create a full backup of your current website.
- disable all plugins except WPML and its add-ons (leave WooCommerce active, too)
- check if the issue is happening again
- if it's not, reactivate your plugins one by one, checking every time if the issue shows up again so that you can understand which plugin is causing that issue
If the issue happens even with the non-WPML plugins disabled:
- leave all the non-WPML plugins deactivated
- switch to a default theme like TwentySeventeen
- try to recreate the issue now