I have a text like the below
[:de] Die BB2 ist eine erlesene türkische Gulet in klassischer Holzbauweise, die alle Annehmlichkeiten und die Eleganz einer exklusiven
Assuming this is your data with the german always before the english, then:
select substring_index(substring_index(col, '[:de]', -1), '[:en]', 1)
If this is not the case, you can test for different possibilities:
select (case when col like '%[:de]%[%:en]%'
then substring_index(substring_index(col, '[:de]', -1), '[:en]', 1)
when col like '%[:de]%[%:]%'
then substring_index(substring_index(col, '[:de]', -1), '[:]', 1)
else substring_index(col, '[:de]', -1)
end)