Your UK employment income will now be taxable in Germany and not the UK. Your employer would need to contact HMRC to seek a direction to operate PAYE. Your employer or their agent can do this by completing the online form here:
Apply for a direction to operate PAYE on an employee's earnings
National Insurance contributions is a separate matter outwith HMRC. You would need to contact the contributions agency on +44 19 1203 7010, as they will be able to answer queries regarding national insurance status and entitlements, pension status and health care provisions for people under United Kingdom pension age who live or work abroad.