The constitutional court can declare laws Or parts of laws as not applicable and can require laws to be made and in specific cases it’s decisions are equivalent to a law (mostly regarding disputes which law applies, state vs. federal law, where certain responsibilities lie and in cases where the constitutional court decides that a law violates the constitution and is immediately declared void.) §31 BVerGG would be the applicable paragraph. There a nice summary in English on the courts own page https://www.bundesverfassungsgericht.de/EN/Verfahren/Wichtig...
At least in my country the law that is ruled unconstitional loses it's power immediately, unless the constitutonal court itself grants some grace period. The thing is: constitutional court can't by itself decide which laws to start analysing next, there must be some formal complaint by either the President, group of members of parliament, or several other institutions, including IIRC any complaint signed by at least 100k citizens.
Edit: added reference to the court page.