you have a CVT box, if you or the previous owner used ATF or any other oil than CVTF - your box is a very expensive paperweight now, Mitsubishi do not sell any parts for this, only the entire transmission.
Too bad you are out of luck. You can use Honda or Eneos CVTF in it without issue. btw a CVT car feels like its out of power - as it never shifts and pegs its rpm on a high range but the vehicle speed is actually increasing.
Did you get a live scan on the transmission done, it shows you the fluid service life, any registered anomaly or slip problems. Before opening an electronic transmission of any kind it is advisable to run complete checks, Read all feedback from the scan and then determine the course of work.