Ik draai de losse schroef vast met de schroevendraaier.

Because the dictionary form is vastdraaien, and that is a separable verb.

In a normal main clause, Dutch puts the conjugated verb in second position, and the separable part goes later in the sentence:

Ik draai de losse schroef vast.

But in other structures, the parts stay together:

• Ik wil de losse schroef vastdraaien.
• Omdat ik de losse schroef vastdraai.
• Ik heb de losse schroef vastgedraaid.

This is a very common Dutch pattern.

Here vast adds the idea of firmly / securely / tight.

So:

• draaien = to turn
• vastdraaien = to tighten by turning

So the sentence is not just about turning the screw; it is about turning it until it is secure.

A useful opposite is losdraaien, which means to loosen / unscrew by turning.

Because losse is the correct adjective form before this noun.

In Dutch, adjectives usually get an -e ending before a noun, especially after de:

• de losse schroef
• de grote tafel
• de nieuwe auto

So de los schroef is incorrect.

More broadly, the basic adjective is los, but before schroef here it becomes losse.

Because schroef and schroevendraaier are both de-words in Dutch.

Dutch singular nouns take either de or het, and this is something you usually have to learn with each noun:

• de schroef
• de schroevendraaier

There is not always a simple rule you can predict from meaning alone, so learners often memorize the article together with the noun.

It is a prepositional phrase introduced by met, and it tells you the instrument used to do the action.

It answers the question:

With what?

So:

• Ik draai de losse schroef vast = the action
• met de schroevendraaier = the tool used for that action

This works very much like English with the screwdriver.

Using de suggests a specific screwdriver is meant, one that is already known from the context.

For example, if there is a particular screwdriver on the table, met de schroevendraaier makes sense.

If you mean with a screwdriver in a more general sense, you could say:

Ik draai de losse schroef vast met een schroevendraaier.

So both are possible, but they are not quite the same.

Yes, that is also a natural sentence.

Dutch word order is somewhat flexible here, especially with separable verbs and prepositional phrases. Both of these are possible:

• Ik draai de losse schroef vast met de schroevendraaier.
• Ik draai de losse schroef met de schroevendraaier vast.

The meaning stays the same. The difference is mostly about rhythm, focus, or what sounds most natural in a particular context.

This is one of the most important things to learn about separable verbs.

In a main clause with a finite verb, the parts split:

• Ik draai de schroef vast.

In an infinitive, they stay together:

• Ik wil de schroef vastdraaien.

In a subordinate clause, they also stay together:

• ... omdat ik de schroef vastdraai.

In the perfect tense, the past participle is:

• vastgedraaid

So:

• Ik heb de losse schroef vastgedraaid.

Because Dutch normally writes compounds as one word.

schroevendraaier is a compound made from smaller parts:

• schroef = screw
• draaier = turner

So literally it is something like screw-turner, which is why it means screwdriver.

This is very normal in Dutch. English often writes such combinations as two words or with a shorter standard word, but Dutch prefers one compound word.

Yes, but there are nuance differences.

• een schroef aandraaien is very common for tightening a screw
• een schroef vastdraaien also means tighten a screw, with a strong sense of making it secure
• iets vastschroeven usually means fasten something with screws

So if you are specifically tightening an already loose screw, vastdraaien or aandraaien are both very natural.

vastschroeven is more often used when you are attaching something by means of screws, not just tightening one screw.