Problem with moving images

Hello, I am using Adobe Premiere Pro 2020 and am trying to make a GTA 5 sort-of loading screen, where there is a background that uses the Basic 3D plugin. Then, there is a character on the front and I want them to move slowly. I make a keyframe for position at the 1st second and 15th second. (the whole thing first comes on screen from the left so its not at the 0 second) For the 15th second, i set the position number to a fairly similar number so it moves slowly but for some reason, the image of the character goes fast during the 15 seconds and it goes a bit farther than its supposed to be and then, it starts slowly returning to its supposed position. Can anyone help me with my problem?

Tldr: Image goes fast when it's supposed to go slowly and it reaches its position goal faster than supposed to so it starts going back