Ui Assist on margin paddin RTL mode

i have problem after i use the RTL mode.
all of my component have margin and padding issues:

i mark it with blue.

by the way how can i use css to change my webapp fonts/colors/padding/margin. ? could not find any guide on vaadin 14.

and i would like size down my grid in order to add more buttons near it, how can i make the grid smaller?

last question how can use the ui to build my app look like that?(not the navbar only the data look the three columnes)

thank you!.