Prior to attempting to deactivate your first proximity mine, go to the Settings and locate movement options.
Identify which key / button makes your character CROUCH, and which key / button toggles between WALK and RUN.
Memorize these settings.

To safely approach an active proximity mine, you must CROUCH and you must be in WALKing speed mode. These two are independent, which many players don't realize. Once you are crouching and moving slowly, simply move directly towards the proximity mine, with your aiming reticle / cursor pointed at the mine.

Once you are close enough, a prompt will appear, telling you to press the Interaction button (typically "E" on keyboard) to deactivate the mine. Press the key or button and the mine will be deactivated. You can then press the same button again to safely take the mine for yourself.