There are multiple definitions - click on the translation that matches your context.

slå fast

verb

full

establish

verb

Definitions of establish

English

(also: found) to start a company, organisation or system, etc

The company was established in 1995.

English

to begin a formal relationship with someone or something, especially a relationship between political or business entities

The new government in Japan was anxious to establish formal diplomatic relations with Korea.

English

to show or prove that something is true

The examination failed to establish a definite cause of death.