Learn Turkish: Bu proje çok yorucu, bu yüzden dinlenmek için hiç fırsatım yok. - This project is very exhausting, therefore I have no opportunity to rest.

You would use keşke and the conditional form of "to be" (olsa). While "I have" is usually expressed with var, counterfactual wishes about having something use olsa (literally: if it were). So you would say: Keşke dinlenmek için fırsatım olsa!

What is the suffix '-ucu' doing in the word yorucu?

It turns the verb yormak (to tire someone) into an adjective. The suffix -ıcı / -ici / -ucu / -ücü creates adjectives that describe what something does. Since yormak means "to tire", yorucu means "tiring" or "exhausting". Another common example is sıkıcı (boring) from sıkmak.

Why is the verb dinlenmek in its full dictionary form (infinitive) before için?

When you want to say "in order to do something" and the subject is general or clear from context, you just use the plain infinitive (-mak / -mek) followed by için. Here, dinlenmek için simply translates to "in order to rest" or "for resting".

I know yüz means "face" or "one hundred". What does bu yüzden mean here?