Looking for logging into the Seite Design Sharepoint site and are not getting the correct working link for it? In such a case, you can use the links given here by searching your desired login page in the search box. If the page is present on our website then you will get all the links related to the Seite Design Sharepoint site. After that you can login as usual with your login credentials.
https://blogs.msdn.microsoft.com/joerg_sinemus/2017/03/03/sharepoint-designer-2013-and-login-issue-in-cloud-scenario/
https://docs.microsoft.com/de-de/sharepoint/dev/general-development/develop-the-site-design-in-sharepoint
https://elczara.wordpress.com/2012/03/09/5-steps-to-create-a-custom-sharepoint-fba-login-page/
https://sharepoint.stackexchange.com/questions/227001/custom-login-page-in-office-365
https://support.office.com/de-de/article/verwalten-ihrer-sharepoint-websiteeinstellungen-8376034d-d0c7-446e-9178-6ab51c58df42
https://support.office.com/de-de/article/verwenden-einer-anderen-seite-f%C3%BCr-die-startseite-ihrer-sharepoint-website-35a5022c-f84a-455d-985e-c691ab5dfa17
https://support.office.com/de-de/article/anpassen-der-gestaltungsvorlage-f%C3%BCr-meine-website-a16c4d51-4284-42f0-a2d6-819289bdc400
https://support.office.com/de-de/article/bei-sharepoint-online-anmelden-324a89ec-e77b-4475-b64a-13a0c14c45ec
https://support.office.com/de-de/article/erstellen-einer-teamwebsite-in-sharepoint-ef10c1e7-15f3-42a3-98aa-b5972711777d
https://support.office.com/en-us/article/customize-a-master-page-to-brand-your-site-0a57b837-4c97-4af9-a088-fedf3dfd1dd5
https://support.office.com/de-de/article/%C3%84ndern-des-aussehens-ihrer-sharepoint-website-06bbadc3-6b04-4a60-9d14-894f6a170818
http://www.canyons.edu/workshop/documents/beginnersguide_sharepoint_webinterface.pdf
https://de.wikipedia.org/wiki/SharePoint