Hi friends , I am newbie here

I am 35 yrs old and riding road bike for 2 years.

I dont like long distances so I dont ride more than 70-80 kms.

My yearly training is around 10000km.Mostly indoor

My average speed is around 30-31km/h on a normal day and on flat terrain.

And I want to improve my avg. speed to 35-36 km/h.

What should I do ? I do cross training (running) ,core stability and weight lifting.

But these dont work.

Pls give me detailed advices to improve myself

Helps appreciated ,thanks