If your battery is draining faster, then we need to see the battery stats. Charge up to 100%, then let it drain to 20-30% with normal usage, without charging in between. Then show us:
1. The main Settings>Battery screen.
2. The fullscreen battery graph screen (which may show Awake time and Cell Signal Strength).
3. The Screen category (to see total Screen On time).
4. The Cell Standby category, if present (to see Time Without Signal).
You might have to install a 3rd party battery monitor, like GSam Battery Monitor, to get the Cell Signal Strength graph.
Considering how old the Note 4 is (and how old any replacement battery for it would be), there's a good chance the battery is just deteriorating due to age.