If a party wins a direct mandate in the National Council election, it will be considered in the second (regional lists) and third (federal lists) calculation procedures regardless of the nationwide votes it receives. Thus, it is not necessary for a party to overcome the 4% threshold, which is typically required to enter the National Council if they have won a direct mandate. Therefore, a direct mandate can be significant.
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There was no threshold in place in 2019.
Plans to reintroduce a threshold for the European elections in 2019 were dropped by the Grand Coalition in November 2018.
https://en.wikipedia.org/wiki/2019_European_Parliament_election_in_Germany#Electoral_threshold
A sperrklausel, also known as a "threshold" or "legal barrier," is a provision in a proportional representation electoral system that excludes parties or lists from the distribution of seats if they receive below a certain percentage of the total votes. Its purpose is to prevent the "fragmentation" of the parliament.
This threshold refers to a rule in the Austrian electoral system that requires political parties to receive at least four percent of the valid votes in a national election in order to be eligible for proportional representation in the parliament.
Für den Einzug in den Landtag muss keine Prozent-Hürde überschritten werden, sondern ein Grundmandat in einem der vier Wahlkreise muss erreicht werden.