Space is unlimited hugeless, so I think it’s impossible that we are the only life in this space. Space is limitless, so I think it’s impossible that we are the only life in space.

Another option for "Space is limitless," is "Space is vast,".

Space is unlimited hugeand vast, so I think it’s impossible that we are the only life in this space. Space is unlimited and vast, so I think it’s impossible that we are the only life in this space.

Huge is good too, personally I prefer "vast" when describing large areas and "huge" for describing large objects

Space is unlimited huge(incredibly vast/limitless/without end), so I think it’s impossible that we are the only life in this space(space/the universe). Space is (incredibly vast/limitless/without end), so I think it’s impossible that we are the only life in (space/the universe).

Generally "in space" has the nuance of "not on earth" in sentences like this, so "in the universe" is probably the more common phrase here

SThe space is unliminfinitedly huge, so I think it’s impossible that we are the only life in this space. The space is infinitely huge, so I think it’s impossible that we are the only life in this space.

Space is unliminfinitedly huge, so I think it’s impossible that we are not the only life in this space. Space is infinitely huge, so I think it’s impossible that we are not the only life in this space.

I’m not sure if they are an intelligent life or not, though. I’m not sure if they are intelligent life or not though.

I’m not sure if they are an intelligent lifespecies or not, though. I’m not sure if they are an intelligent species or not, though.

I’m not sure they are anwhether they would be intelligent life or not, though. I’m not sure whether they would be intelligent or not, though.

"whether [condition] or not" is a common pattern "whether" is used to list alternate possibilities - if one is true then the other is not. In this case the lifeforms are either intelligent or not.

Though I’m not sure if they are an intelligent form of life or not, though. Though I’m not sure if they are an intelligent form of life or not.

I can’t wait to progressfor space exploration likto progress like the Mars project. I can’t wait for space exploration to progress like the Mars project.

I can’t wait to progress space exploration likthrough things like the Mars project. I can’t wait to progress space exploration through things like the Mars project.

I can’t wait tofor progress in space exploration, like the Mars project. I can’t wait for progress in space exploration, like the Mars project.

Here saying "I can't wait to progress space exploration" makes it sound like you yourself would be the one causing progress in that area. Instead you should phrase it in a passive way

I can’t wait to progress space exploration like Mars project. I can’t wait to progress space exploration like Mars project.

I can’t wait to progress space exploration like the Mars project. I can’t wait to progress space exploration like the Mars project.