Gitlab registry Docker login: x509: certificate signed by unknown authority

Hi Guyes,

i am trying to host my own Gitlab on my Synology-NAS using Docker.
I have the following containers: Gitlab-ce / registry / gitlab-runner

everything is working so far i even can connect my gitlab from outside because i use the reverse proxy

but wen i want to login to my registry using

docker login https://mydomain.synology.me:5050

i got the error from the title of this post after entering username and password

i have tryed a lot with certificate copieng and creating and whatever.
i also followed this post step by step:
https://forum.gitlab.com/t/gitlab-runner-x509-certificate-signed-by-unknown-authority/32403

#letsencryptstuff
letsencrypt['enable'] = true
letsencrypt['contact_emails'] = ['mydomain@gmail.com'] # This should be an array of email addresses to add as contacts
letsencrypt['auto_renew'] = true
letsencrypt['auto_renew_hour'] = "6"
letsencrypt['auto_renew_day_of_month'] = "*/7"

#NewConfig
external_url 'https://mydomain.synology.me:10000'

mattermost_nginx['listen_addresses'] = ['*', '[::]']
pages_nginx['listen_addresses'] = ['*', '[::]']
nginx['listen_addresses'] = ["0.0.0.0", "[::]"]
nginx['listen_port'] = 80
nginx['listen_https'] = false
nginx['redirect_http_to_https'] = false
mattermost_nginx['redirect_http_to_https'] = false

registry_external_url 'https://mydomain.synology.me:5050'
gitlab_rails['registry_enabled'] = true
gitlab_rails['registry_host'] = "mydomain.synology.me"
gitlab_rails['registry_port'] = "5050"
#gitlab_rails['registry_path'] = "/var/opt/gitlab/gitlab-rails/shared/registry"

registry_nginx['listen_addresses'] = ['*', '[::]']
registry_nginx['redirect_http_to_https'] = false
registry_nginx['ssl_certificate'] = "/etc/gitlab/ssl/mydomain.synology.me/fullchain.pem"
registry_nginx['ssl_certificate_key'] = "/etc/gitlab/ssl/mydomain.synology.me/privkey.pem"