Hi i looked at the score could not figure out what is the time signature it looks as though each bar is different and that there is not one. Am i correct?
It's in 4/4, as the C at the beginning tells us that. Whilst it is said to stand for common time - there are far, far more pieces in 4/4/ than any other time sig. - it's actually a broken circle. History tells us that long ago, religious stuff was in 3 time, representing the Holy Trinity, and signified with a circle. 4/4 came along, and the circle was broken.
You may have been confused by the groups of 3 quavers in Mahler's work. Some are purely that, worth a beat and a half, while others having a '3' under them. Those are triplets and take up the time of one beat (crotchet, quarter). Every bar works out to have the 4 beats that the 'C' at the beginning asks for.