I started learning maui a couple of days ago. I'm making an app on pixel 9 pro emulator, but when I run my app on samsung s21 fe, the interface gets too big. Below I will attach the maui script and photos. (I connect to s 21 fe via cable and don’t use an emulator)
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage BackgroundColor="#DCEBFF"
xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="Interval_Jogging.MainPage"
xmlns:toolkit="http://schemas.microsoft.com/dotnet/2022/maui/toolkit"
Shell.BackgroundColor="#DCEBFF">
<ContentPage.Behaviors>
<toolkit:StatusBarBehavior
StatusBarColor="#DCEBFF"
StatusBarStyle="DarkContent"/>
</ContentPage.Behaviors>
<Grid>
<Button
x:Name="MenuBtn1"
VerticalOptions="End"
HorizontalOptions="Center"
WidthRequest="150" HeightRequest="80"
CornerRadius="50"
Margin="0, 0, 0, 30"
BackgroundColor="#AFC3FF" />
<RoundRectangle
x:Name="Rect"
WidthRequest="370" HeightRequest="390"
Margin="0, 0, 0, 90"
CornerRadius="50"
BackgroundColor="#AFC3FF" />
<RoundRectangle
x:Name="Rect1"
VerticalOptions="Center"
HorizontalOptions="Center"
WidthRequest="370"
HeightRequest="300"
CornerRadius="50">
<RoundRectangle.Background>
<LinearGradientBrush StartPoint="0,0" EndPoint="1,0">
<GradientStop Color="#406BEB" Offset="0.0" />
<GradientStop Color="#5F87FF" Offset="1.0" />
</LinearGradientBrush>
</RoundRectangle.Background>
</RoundRectangle>
<Label
x:Name="Walk_RunText"
VerticalOptions="Center"
HorizontalOptions="Center"
Margin="0, 0, 0, 220"
FontFamily="ClimateRegular"
FontSize="60"
TextColor="White"
Text="Walk"/>
<Image
x:Name="Walk_RunImg"
VerticalOptions="Center"
HorizontalOptions="Center"
Margin="0, 70, 0, 0"
Scale="0.5"
Source="icon_walk.png"/>
<Label
x:Name="TimerText"
VerticalOptions="Center"
HorizontalOptions="Center"
Margin="0, 0, 0, 390"
FontFamily="LexendBold"
FontSize="75"
TextColor="#436DED"
Text="00:00:30"/>
<Button
x:Name="PauseBtn"
VerticalOptions="Center"
HorizontalOptions="Center"
WidthRequest="175" HeightRequest="80"
CornerRadius="50"
Margin="0, 420, 195, 0"
Text="PAUSE"
FontFamily="LexendBold"
FontSize="35"
TextColor="#436DED"
BackgroundColor="#AFC3FF" />
<Button
x:Name="StopBtn"
VerticalOptions="Center"
HorizontalOptions="Center"
WidthRequest="175" HeightRequest="80"
CornerRadius="50"
Margin="195, 420, 0, 0"
Text="STOP"
FontFamily="LexendBold"
FontSize="35"
TextColor="#B55354"
BackgroundColor="#E5A2A2" />
<RoundRectangle
x:Name="WorkoutTime"
VerticalOptions="Center"
HorizontalOptions="Center"
WidthRequest="190" HeightRequest="80"
CornerRadius="50"
Margin="0, 0, 180, 600"
BackgroundColor="#AFC3FF" />
</Grid>
</ContentPage>

As I mentioned earlier, I started learning maui quite recently and I don’t know what to do at all. I didn't find the answer anywhere.
widthRequest=100, useGridorFlexLayout, so you can divide the screen width between items in each row. Then margins or padding to make gaps between items.