Problem with foreach powershell

As you have already been told in the comments, when you nest a foreach for the uris within a foreach for the names of the files, you are combining all the file names with all the uris. That is, in the end four calls are being made to Invoke-WebRequest equivalent to:

Invoke-WebRequest "https://dl.google.com..." -OutFile $destino\"googlechromestandaloneenterprise64.msi"

Invoke-WebRequest "https://www.winrar.es/descargas/103" -OutFile $destino\"googlechromestandaloneenterprise64.msi"

Invoke-WebRequest "https://dl.google.com..." -OutFile $destino\"Winrar.exe"

Invoke-WebRequest "https://www.winrar.es/descargas/103" -OutFile $destino\"Winrar.exe"

What I think you have to do is create an array in which each element has the information you need to perform a download, that is, url and local file where to download. It would look like this:

$ficherosADescargar=@();
$ficherosADescargar+= [PSCustomObject] @{
Uri="https://dl.google.com/tag/s/appguid%3D%7B8A69D345-D564-463C-AFF1-A69D9E530F96%7D%26iid%3D%7B03FE9563-80F9-119F-DA3D-72FBBB94BC26%7D%26lang%3Den%26browser%3D4%26usagestats%3D0%26appname%3DGoogle%2520Chrome%26needsadmin%3Dprefers%26ap%3Dx64-stable/dl/chrome/install/googlechromestandaloneenterprise64.msi"
Destino="googlechromestandaloneenterprise64.msi"}

$ficherosADescargar+= [PSCustomObject] @{
Uri="https://www.winrar.es/descargas/103"
Destino="Winrar.exe"}

Foreach($ficheroADescargar in $ficherosADescargar){
    Invoke-WebRequest $($ficheroADescargar.Uri) -OutFile (Join-Path $destino $ficheroADescargar.Destino)
}

As general recommendations:

  

This is the final execution of the Script

< # Download and installation                     Ninja install     # >

<#ROOT#>

param([switch]$elevated)

function Test-Admin {
   $currentUser = New-Object Security.Principal.WindowsPrincipal $([Security.Principal.WindowsIdentity]::GetCurrent()) 
   $currentUser.IsInRole([Security.Principal.WindowsBuiltinRole]::Administrator) 
}

if((Test-Admin) -eq $false){
    if($elevated){
        echo "Permisos no concedidos"
    }else{
        Start-Process powershell.exe -Verb RunAs -ArgumentList ('-noprofile -noexit -file "{0}" -elevated' -f ($myinvocation.MyCommand.Definition)) 
    }
    exit
}

echo "Previlegios concedidos"

#Establecemos la ruta de descarga
$descargas = "C:\Dune"

#Primero comprobamos si el directorio existe
#De caso cotrario el directorio se va a crear según la rura establecida
if(Test-Path -Path $descargas -PathType Container){
    Write-Host "El directorio $descargas ya esxiste" -ForegroundColor Yellow
}else{
    Write-Host "Creando directorio $descargas" -ForegroundColor Green
    New-Item -Path $descargas -ItemType directory
}

#Ruta destino "Join-Path", compondremos la ruta
$destino = "$descargas"

#creamos un array en el que cada elemento tenga la información que necesitamos para realizar una descarga.
#Uri y Destino( Ruta de la descarga )
$ficherosADescargar=@();

<#     Inicio elementos array     #>

$ficherosADescargar+= [PSCustomObject] @{
Uri="https://dl.google.com/tag/s/appguid%3D%7B8A69D345-D564-463C-AFF1-A69D9E530F96%7D%26iid%3D%7B03FE9563-80F9-119F-DA3D-72FBBB94BC26%7D%26lang%3Den%26browser%3D4%26usagestats%3D0%26appname%3DGoogle%2520Chrome%26needsadmin%3Dprefers%26ap%3Dx64-stable/dl/chrome/install/googlechromestandaloneenterprise64.msi"
Destino="googlechromestandaloneenterprise64.msi"}


$ficherosADescargar+= [PSCustomObject] @{
Uri="http://rarlab.com/rar/winrar-x64-540.exe"
Destino="Winrar.exe"}

$ficherosADescargar+= [PSCustomObject] @{
Uri="https://download.mozilla.org/?product=firefox-latest-ssl&os=win64&lang=es-ES"
Destino="Firefox.exe"
}

$ficherosADescargar+= [PSCustomObject] @{
Uri="http://descargar.raanmavi.com/adobe-reader-dc-offline"
Destino="AdobeReaderOfflineInstaller.exe"
}

$ficherosADescargar+= [PSCustomObject] @{
Uri="https://fpdownload.macromedia.com/pub/labs/flashruntimes/flashplayer/install_flash_player.exe"
Destino="FlashPlayerChrome.exe"
}

$ficherosADescargar+= [PSCustomObject] @{
Uri="https://fpdownload.macromedia.com/pub/labs/flashruntimes/flashplayer/install_flash_player_ppapi.exe"
Destino="FlashPlayerFirefox.exe"
}


<#     Fin elementos array     #>

#Array de ejecutables .exe .msi
$ejecutables=@()

#Recorremos cada elemento del array
Foreach($ficheroADescargar in $ficherosADescargar){
    #Descarga de ficheros
    Invoke-WebRequest $($ficheroADescargar.Uri) -OutFile (Join-Path $destino $ficheroADescargar.Destino)
    #Instalación de ficheros
    $ejecutables += Join-Path $destino $ficheroADescargar.Destino
}


ForEach($variable in $ejecutables){
   #Argumentos para la instalación
   $MSIargumentos=@(
                 "/i"
                 ('"{0}"' -f $variable)
                 "/passive"
                 "/L*V"
                 "C:\Dune\install.log"
                 )

    #Iniciamos la instalación de los programas
    if($variable -like '*.msi' ){
        Start-Process msiexec.exe -ArgumentList $MSIargumentos -Wait
    }else{
        if( $variable -like "*AdobeReaderOfflineInstaller.exe*"){
            Start-Process -FilePath  ('"{0}"' -f $variable) -ArgumentList "/sAll /rs /rps /msi /norestart /quiet EULA_ACCEPT=YES" -PassThru  -Wait

        }else{
            Start-Process -FilePath  ('"{0}"' -f $variable) -ArgumentList "/S" -PassThru  -Wait
        }
    }
}

remove-item C:\Dune\*.* -Exclude *.log

Write-Host -Fore Green "La instalación ha terminado !!!!!!!"