Die heissen beide "Spannung" daher die Verwirrung, gel?

Tension can be taken literally or figuratively, like "Spannung"
literally: decribes the potential energy within an object or created by one object or objects on another- "The rope between the doors was under alot of tension"
figuratively: describes a general sense of stress or "unstimmigkeit" "There was tension between the two of them, which gave her a tension headache"

suspense only has one variant of meaning and means a tension GENERATED BY THE UNKOWN, OR NOT KNOWING WHAT IS COMING
(in a completely different vein, "suspense" can also mean "Frist")

The particular property of "suspense" is that the course of action is "suspended", i.e. the action does not continue but comes to a virtual standstill.