Using an Apple watch with Iphone SE

Dear all,

Today I bought a second hand Apple watch 2 to use with my corporate mobile Iphone SE. After several unsuccessful connection trials I realized that the watchos 6 is not compitable with ios 12.4 which is the latest ios version of SE.

I’m trying to find a way to connect the watch to SE. Is there any way to downgrade watchos back to 5, some other solution to connect devices?

Thx in advance