For those, who could face with something, like I did, that worked for me. I manually change column width:
<controls:FlowListView x:Name="ReposList" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand" FlowItemsSource="{Binding PrivateNews.Result}" HasUnevenRows="True" FlowColumnCount="1" Margin="15, 15, 15, 0"><controls:FlowListView.FlowColumnTemplate><DataTemplate><Grid VerticalOptions="Start" HorizontalOptions="Start" Margin="0, 0, 0, 20" ColumnSpacing="0" RowSpacing="5"><Grid.ColumnDefinitions><ColumnDefinition Width="33"/><ColumnDefinition Width="20"/><ColumnDefinition Width="{Binding Source={x:Reference Name=ReposList}, Path=BindingContext.ColumnWidth}"/></Grid.ColumnDefinitions><Grid.RowDefinitions><RowDefinition Height="Auto"/><RowDefinition Height="20"/></Grid.RowDefinitions><Image x:Name="Avatar" Source="{Binding ImageUrl}" HeightRequest="30" WidthRequest="30" Grid.Column="0" Grid.Row="0" Grid.RowSpan="2" VerticalOptions="Start" HorizontalOptions="Start" Margin="0, 5, 5, 0"/><StackLayout Grid.Column="1" Grid.Row="0" Grid.ColumnSpan="2" VerticalOptions="FillAndExpand" HorizontalOptions="FillAndExpand" BackgroundColor="Aqua"><Label x:Name="Title" FormattedText="{Binding CustomFormattedText}" TextColor="Black" LineBreakMode="CharacterWrap"/></StackLayout><customClasses:FontIcon x:Name="ActionTypeIcon" Text="{Binding ActionTypeFontIcon}" TextColor="Gray" FontSize="16" FontFamily="Octicons" Grid.Column="1" Grid.Row="1" VerticalOptions="Center" HorizontalOptions="StartAndExpand" Margin="0, 0, 5, 0"/><Label x:Name="PublishedTime" Text="{Binding Published}" FontSize="14" Grid.Column="2" VerticalOptions="Center" HorizontalOptions="FillAndExpand" Grid.Row="1"/></Grid></DataTemplate></controls:FlowListView.FlowColumnTemplate></controls:FlowListView>How to get screen width and other stuff you can find on the internet.