Learn Turkish: Fırtınadan önce yeleği sıkıca bağlamak lazımdı. - It was necessary to tie the vest tightly before the storm.

We use the full dictionary form of the verb, bağlamak (to tie), and follow it with lazım (necessary) plus the past tense ending -dı. Together, bağlamak lazımdı means it was necessary to tie or one had to tie.

Why does fırtına have the -dan ending before önce?

In Turkish, the word önce (before) always requires the word before it to take the ablative or from case ending. So before the storm is structured logically as from the storm before (fırtınadan önce).

What happened to the dictionary word for vest (yelek) in this sentence?

Because the sentence is about tying a specific vest (the vest), it needs the specific direct object ending (the accusative case -i). When a vowel is added to a word ending in k, the k usually softens to a soft g (ğ). That is why yelek becomes yeleği.

How is the word sıkıca (tightly) formed?

The base word is the adjective sıkı (tight). Adding the suffix -ca (or -ce depending on vowel harmony) turns the adjective into an adverb, changing the meaning to tightly or in a tight manner.