Is there any evidence supporting that mars may have had life at one time?

there are several lines of evidence which support the idea, but do not demonstrate it. Demonstration (proof) requires unequivocal remains of once-living things. Some have suggested a biological origin for features observed in a Mars-derived meteorite, but the features are not definitely biological in origin. They simply could be (although I do not think that they are). Otherwise, there are no "fossils" that have ever been observed (identified) from Mars samples or images. And that is the only way to prove the existence of life in the past.

None so far. The Viking landers looked for existing life; it didn't find any. The Curiosity rover isn't looking for past life directly, but it would be sensitive enough to pick up any tell-tale chemicals of past life - but, as stated... it hasn't found any. Yet.

Running water, that it had a reasonably think atmosphere, the seasonal presence of methane, those are good signs.

Not yet.

THAT is why we NEED to sned a manned mission there

No