Image on Slider to resize

can you please tell me the precise size for the image slider.

Hello,
By default slider height is set to 100vh. This means slider will take 100% of the screen height.
And full screen width.

You can change slider height by adding below CSS codes in:
Tara Theme Settings -> Insert Codes -> CSS Codes

#slider,
.home-slider {
	min-height: 70vh;
}
.owl-item {
	height: 70vh;
}

70vh means 70% of screen height. Change this value as you want.

And clear cache after adding css codes.

example.com/admin/config/development/performance

can you please tell me the precise size for the image slider.

For background images, the best size is 1920px wide x 1080px high. This ideal ratio of 16:9