I dug a little deeper into the database. It seems that most modifications have to be made to the FactTypeTable by keeping the FactTypeID:
sqlite> .schema FactTypeTable
CREATE TABLE FactTypeTable (FactTypeID INTEGER PRIMARY KEY, OwnerType INTEGER, Name TEXT COLLATE RMNOCASE, Abbrev TEXT, GedcomTag TEXT, UseValue INTEGER, UseDate INTEGER, UsePlace INTEGER, Sentence BLOB, Flags INTEGER );
CREATE INDEX idxFactTypeName ON FactTypeTable (Name);
CREATE INDEX idxFactTypeAbbrev ON FactTypeTable (Abbrev);
CREATE INDEX idxFactTypeGedcomTag ON FactTypeTable (GedcomTag);
sqlite> select * from FactTypeTable limit 20;
1|0| Birth |Birth|BIRT|0|1 |1|[person] was born< [Date]>< [PlaceDetails]>< [Place]>.|-1
2|0| Death |Death|DEAT|1|1 |1|[person] died< [Desc]>< [Date]>< [person:Age]>< [PlaceDetails]>< [Place]>.|-1
3|0|Christen|Chr|CHR|0|1|1|[person] was christened< [Date]>< [PlaceDetails]>< [Place]>.|-1
4|0|Burial|Burial|BURI|0|1|1|[person] was buried< [Date]>< [PlaceDetails]>< [Place]>.|-1
5|0|Cremation|Cremation|CREM|0|1|1|[person] was cremated< [Date]>< [PlaceDetails]>< [Place]>.|-1
6|0|Adoption|Adoption|ADOP|0|1|1|[person] was adopted< [Date]>< [PlaceDetails]>< [Place]>.|-1
7|0|Baptism|Baptism|BAPM|0|1|1|[person] was baptized< [Date]>< [PlaceDetails]>< [Place]>.|-1
8|0|Bar Mitzvah|Bar Mitzvah|BARM|0|1|1|[person] celebrated his bar mitzvah< [Date]>< [PlaceDetails]>< [Place]>.|-1
9|0|Bas Mitzvah|Bas Mitzvah|BASM|0|1|1|[person] celebrated her bas mitzvah< [Date]>< [PlaceDetails]>< [Place]>.|-1
10|0|Blessing|Blessing|BLES|0|1|1|[person] was blessed< [Date]>< [PlaceDetails]>< [Place]>.|-1
11|0|Christen (adult)|Chr (adult)|CHRA|0|1|1|[person] was christened< [Date]>< [PlaceDetails]>< [Place]>.|-1
12|0|Confirmation|Confirmation|CONF|0|1|1|[person] was confirmed< [Date]>< [PlaceDetails]>< [Place]>.|-1
13|0|First communion|First comm|FCOM|0|1|1|[person] received first communion< [Date]>< [PlaceDetails]>< [Place]>.|-1
14|0|Ordination|Ordination|ORDN|0|1|1|[person] was ordained< [Date]>< [PlaceDetails]>< [Place]>.|-1
15|0|Naturalization|Naturalization|NATU|0|1|1|[person] was naturalized< [Date]>< [PlaceDetails]>< [Place]>.|-1
16|0|Emigration|Emigration|EMIG|0|1|1|[person] emigrated< [Date]>< from [Place:plain]>< [PlaceDetails]>.|-1
17|0|Immigration|Immigration|IMMI|0|1|1|[person] immigrated< [Date]>< to [Place:plain]>< [PlaceDetails]>.|-1
18|0|Census|Census|CENS|0|1|1|[person] appeared in the census< [Date]>< [PlaceDetails]>< [Place]>.|-1
19|0|Probate|Probate|PROB|0|1|1|[person] had [person:hisher] estate probated< [Date]>< [PlaceDetails]>< [Place]>.|-1
20|0|Will|Will|WILL|0|1|1|[person] signed a will< [Date]>< [PlaceDetails]>< [Place]>.|-1
So maybe it's more "a patch against the database" (keeping the UI in english - which is fine).
If you confirm that it's safe to modify the corrosponding fields in the DB, I'd provide a translation to german.