docs: avoid sloppy language. Throu -> trough; dangling adverb 'first'…

[jnweiger]

More formal language:

• Throu -> trough (3 instances)
• backstab -> step back
• dangling adverb 'first' moved to its verb.

[mmattel]

~Backport to 5.0~

The base of this PR was not master but another PR which is not merged. We therefore have to recreate the changes for 5.0 🤦‍♂️