Don't worry about being new, we all have to start sometime. You are also picking some rather difficult phrases to start with.

You have a lot of the right bits, but they are not necessarily strung together correctly. The first thing to understand about Quenya is that pronominal subject (like "we") are attached to the verb as suffixes (such as lve). So "we have" would be haryalve not lwe harya.

Also, harya- as a verb means "have" in the sense of "to possess", so doesn't really fit what you are trying to say. You really want "have to" in the sense of "must do". I've seen the sense "must" in Quenya expressed with the verb mauya- "to impel", but in this case I think the verb pol- = "can, be able" is closer to the correct sentiment. I would also use the verb cil- "choose" instead of the noun úvie "consideration".

polelve cile = "We can (are able to) choose..."

Rather than illi "all", I would use the adverb rie "only", which is less ambiguous. The verb car- "to make, do, act" is a good fit, when combined with the conjunction manen "how":

polelve rie cile manen care = "We can only choose how to act..."

The preposition yó means "together with", as in "I went to the store with John". You want something more like the preposition le, I think, or perhaps the instrumental.

polelve rie cile manen care le i lúme = "We can only choose how to act with the time..."

This passive construction "is given to us" is also tricky. I think the least ambiguous way to do it is to use the passive participle antaina "given". Also, it is more natural Quenya to use an the indirect (dative) object ven instead of the prepositional na ve.

Thus:

polelve rie cile manen care le i lúme ya na antaina ven = "We can only choose how to act with the time that is given to us"

I think that's reasonably close to the Gandalf's original sentiment.

+Paul Strack one small comment : the correct conjugation would be polilve

+Tamas Ferencz Oh yes, duh, thank you. I am not sure what I was thinking.

Instead of "how to act" manen care, what to do would be? Mana care?

Also, would it not be carina instead of care?

You are correct, "what to do" would be mana care, which might work just as well as manen care.

As for carina, that's the passive participle of car- with a meaning like "done, made, built". It is an adjective. In this case the infinitive care "to do, to act" fits better.

Gotcha! Thank you for the help! I think I'm slowly picking it up

there is also carna as participle of car-, right?

+Forthianor I indeed, but as far as I can see it is only attested as part of alacarna eldamo.org - Eldamo : Quenya : alacarna
(and the EQ ilkarna). This does not invalidate it necessarily though.

Instead of care le i lúme ("do with the time") , how about saying care i lúmessë ("do in the time")? In my opinion, that still fits the intended meaning well.

+Jan Sorondil Slaný Sure that works. I'd also suggest the instrumental as a possibility: care i lúmenen "do by means of the time".

I'd prefer the instrumental, but just because I like the way it makes look words :)
+Tamas Ferencz Hey, I know that, but I'm kinda a vinquenya speaker, even if I gotta admit I need to updated my knowledge on the topic. Do you have any suggestions on where I can find some good and new material on Quenya grammar?

+Forthianor I I don't know of any recent material (except for reading through the last 5 Parma Eldalamberon issues). But I am in the process of writing one - will be done in a few months I guess.