Quick answers
How do I revive a teammate?
Walk to their statue and hold F (Square/X). Picking the statue up first (tap F) lets you carry it to cover before reviving.
What key is the specialization?
Q on keyboard and L1/LB on controller. It is the class-defining ability: Light gets grapple or cloak, Medium the heal beam or turret, Heavy the mesh shield or charge.
How do I slide?
Sprint and tap Left Ctrl (Circle/B). Sliding down slopes keeps speed and lets you shoot; jumping out of a slide preserves momentum.
How do I use the zipline?
Jump into it with Space (Cross/A); press Space again to drop. You can shoot while riding.
Can I rebind gadgets?
Yes: Settings › Controls › Gadget 1–3. Many players put the most used gadget on a mouse side button and keep the others on E and C.