PS + CSOM to import search schema XML (e.g. managed property definitions)..

ImportSearchSchema.ps1

. .\TopOfScript.ps1

# need some extra types bringing in for this script..
Add-Type -Path "c:\Program Files\Common Files\microsoft shared\Web Server Extensions\15\ISAPI\Microsoft.SharePoint.Client.Search.dll"

# TODO: replace this path with yours..
$pathToSearchSchemaXmlFile = "C:\COB\Cloud\PS_CSOM\XML\COB_TenantSearchConfiguration.xml"
# we can work with search config at the tenancy or site collection level:
#$configScope = "SPSiteSubscription"
$configScope = "SPSite"

$searchConfigurationPortability = New-Object Microsoft.SharePoint.Client.Search.Portability.SearchConfigurationPortability($clientContext)
$owner = New-Object Microsoft.SharePoint.Client.Search.Administration.SearchObjectOwner($clientContext, $configScope)
	
[xml]$searchConfigXml = Get-Content $pathToSearchSchemaXmlFile
$searchConfigurationPortability.ImportSearchConfiguration($owner, $searchConfigXml.OuterXml)
$clientContext.ExecuteQuery()

Write-Host "Search configuration imported" -ForegroundColor Green

When i try to run this script I get the following error when executing "$searchConfigurationPortability = New-Object Microsoft.SharePoint.Client.Search.Portability.SearchConfigurationPortability($clientContext)" :

New-Object : Cannot find an overload for "SearchConfigurationPortability" and the argument count: "1".
At D:\Install\CDMS_Release_1.2_20150421_084744\SetUpManagedProperties.ps1:33 char:35

• $searchConfigurationPortability = New-Object Microsoft.SharePoint.Client.Search. ...

• - CategoryInfo          : InvalidOperation: (:) [New-Object], MethodException
  - FullyQualifiedErrorId : ConstructorInvokedThrowException,Microsoft.PowerShell.Commands.NewObjectCommand
  
  

Do you know what to do in this case?

You are using mixed versions of the CSOM library dlls. Make sure they are the same version 15 vs 16, etc.