Learn Arabic (Modern Standard): ليس عندنا حل.

In Arabic, "we have" is expressed as عندنا (literally "with us"). To say "we do not have", you simply place ليس in front of it. The literal translation of the whole sentence is "there is not with us a solution."

Why do we use ليس instead of the "we" form (لسنا)?

When expressing possession, ليس agrees with the thing you do not have, not the person who lacks it. The thing we don't have here is حل (a solution), which is a masculine noun. Therefore, we use the default masculine form ليس. If we lacked a feminine object, like a car (سيارة), we would use the feminine form ليست.

Why is حل (a solution) at the very end of the sentence?

In Arabic, if the main subject is indefinite (meaning it is "a solution" instead of "the solution"), it must come after the prepositional phrase. Since حل has no "al-" (the) attached to it, it gets pushed to the end, after عندنا.

What exactly is the word عندنا made of?

It is a combination of the word عند (with/at) and the attached pronoun نا (us/our). Together, they form "with us", which is the standard way to say "we have" in Arabic.