Multilang version of CMSMS by Katon - problems with breadcrumb and selflink navi

[sparky]

Katon's multilang version works fine. I have a splash page where either 'German' or 'English' can be selected. When selecting the English homepage, the suffix '&lan=en' is added to the URL. So far so good. However, when clicking on the breadcrumb or selflink (next page / previous page) navigation the suffix '&lan=en' is not added to the URL. Consequently the link then leads to the default language page, which in my case is German.

I assume that the two php files function.breadcrumbs.php and function.cms_selflink.php must be modified but I don't know how. Can somebody help? Thanks.