I have a 1500 Suzuki intruder that I changed oil oil filter and gear lube on Plus changed plugs now when I put it in first it dies why
I am unfamiliar with this motorcycle.
Many or most of today's bikes, however, are designed to allow the transmission to be shifted into gear only when the clutch is disengaged, i.e., when the rider is squeezing the clutch lever on the handlebar. If the bike thinks the clutch lever isn't being squeezed, then it cuts the motor as the rider attempts to shift into gear. (Some bikes also have a similar switch on the sidestand: attempting to put the bike in gear with the sidestand down will likewise kill the motor.)
If the bike starts and idles correctly, and immediately dies when the clutch is squeezed to shift into first, then something is awry in the clutch (or sidestand) safety circuit. Somewhere on the clutch lever is a small switch, and either that switch has broken and is stuck in the position that indicates "clutch is engaged," or there's a fault in the wiring or connectors downstream from the switch.
A good search approach when something fails just after work is done is "Look where you worked." It's very possible you inadvertently disturbed the clutch safety switch wiring or a connection when you were working on the bike.
The fault will have to be found and rectified.