How to style a Button in Xamarin.Forms using CSS?

I have added a button from xaml file like that:

<ContentView.Content>
   <Button Image="{Binding Icon}" Text="{Binding Title}" Clicked="ClickEvent" HeightRequest="10"  WidthRequest="10" />
</ContentView.Content>

How can I style the button to look like this?

I have css file in my xamarin project but I dont seem to reach Button image with it sucessfully because such code gives no result:

.button img {
    height: 50px;
    width: 50px;
}

My current result of a button (terrible), picture is way to big:

To be able to fully customize a button like that, it's probably best to implement your own Button control instead of using CSS:

XAML

<?xml version="1.0" encoding="UTF-8"?>
<ContentView xmlns="http://xamarin.com/schemas/2014/forms" 
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="YourApp.Views.SomeRoundImageButton">

  <Frame
    CornerRadius="8">
    <Grid
      RowDefinitions="2*,*">
      <Image
        Grid.Row="0"
        Source="{Binding Icon}"/>
      <Label
        Grid.Row="1"
        TextColor="Blue"
        Text="{Binding Title}"/>      
    </Grid>
    <Frame.GestureRecognizers>
      <TapGestureRecognizer
        Tapped="OnButtonTapped"/>
    </Frame.GestureRecognizers>
  </Frame>

</ContentView>

Code-behind

using System;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;

namespace YourApp.Views {
    [XamlCompilation(XamlCompilationOptions.Compile)]
    public partial class SomeRoundImageButton : ContentView {

        public string Title {
            get => (string)GetValue(TitleProperty);
            set => SetValue(TitleProperty, value);
        }

        public ImageSource Icon {
            get => (ImageSource)GetValue(IconProperty);
            set => SetValue(IconProperty, value);
        }

        public event EventHandler<EventArgs> ButtonTapped;

        public static readonly BindableProperty TitleProperty = BindableProperty.Create(nameof(Title), typeof(string), typeof(SomeRoundImageButton));
        public static readonly BindableProperty IconProperty = BindableProperty.Create(nameof(Icon), typeof(ImageSource), typeof(SomeRoundImageButton));

        public SomeRoundImageButton() {
            InitializeComponent();
            BindingContext = this;
        }

        private void OnButtonTapped(object sender, EventArgs e) {
            ButtonTapped?.Invoke(this, e);
        }
    }
}

Usage

<ContentView.Content>
    <StackLayout>
        <views:SomeRoundImageButton
          Icon="{Binding Icon}"
          Title="{Binding Title}"
          WidthRequest="80"
          HeightRequest="80"
          ButtonTapped="Clicked"/>
    </StackLayout>
</ContentView.Content>

This gives you a lot more freedom for your design, you can make the Image bigger or smaller, add more lines of text to the Label, define the size of the CornerRadius, set all kinds of other properties...

Obviously, you need to play around with it to figure out the intended design, but I hope this will be of help. Note, this is just one way of doing this. In Xamarin.Forms (and .NET MAUI), there are many ways of achieving the same things.