Oracle - Should processes limit be lower than sessions parameter
The value of sessions can not be lower than processes by definition. Even if you try to set it, the database will just ignore it:
SESSIONS

Default value Derived: (1.5 * PROCESSES) + 22
Oracle uses the default value of this parameter as its minimum. Values
between 1 and the default do not trigger errors, but Oracle ignores
them and uses the default instead.

You simply hit the process limit for that instance. Increase the limit accordingly, or investigate what application opened/opens these sessions.
Also the number of sessions for users should be limited by their profile, not the instance level sessions parameter.
CREATE PROFILE - look for SESSIONS_PER_USER.