Orbiting 101

Prograde “forward” burn (blue): increase speed, raise/widen orbit and leave.

Retrograde “reverse” burn (red): slow down, lower/tighten orbit and fall on a body.

Burning at periapsis (the “peak”) moves apoapsis (opposite point) directly towards/away wrt. planet center.

The orbiter always wants to crash land onto something. So your goal is to miss the surface while falling at it.