Learn Turkish: Bu şişeyi tekrar kullandığım için yeni bir şişe almıyorum. - Because I use this bottle again, I am not buying a new bottle.

This is the structure you are currently learning! We take the verb root kullan (use), add the -dık suffix (which softens to -dığ because a vowel comes next), and then add the "my" possessive ending -ım. Together with için, kullandığım için literally translates to something like "for my using", but in natural English, it means "because I use".

How do we know kullandığım için means "because I use" and not "because I used"?

The -dık + possessive + için structure can refer to the past or the present. You have to look at the main verb of the sentence to know which one it is. Since the main verb here is almıyorum (I am not buying - present continuous), we know the "using" is also an ongoing, present action.

Why does the first part say şişeyi but the second part just says şişe?

This is a great reminder of how the accusative case works. Bu şişeyi means "this specific bottle," so it needs the specific direct object ending -yi. In the second half, yeni bir şişe means "a new bottle" (any new bottle, not a specific one), so it remains in its plain form without the accusative ending.

I thought almak meant "to take". Why is it translated as "buying" here in almıyorum?