response.Position := 0; // !!!
memo1.Lines.LoadFromStream(response);

type
   THttpRequestType  = (rqPost, rqGet);

   function SendHttpRequest(AHttpRequestType: THttpRequestType;
                            const AURL, APOSTData: string;
                            const AResponse: TStream;
                            var AErrMsg: string;
                            const AHttpUserName: string = '';
                            const AHttpPassword: string = '';
                            AAsMozillaUserAgent: boolean = false;
                            AAnotherHeaderLines: TStrings = nil;
                            const AProxyServerIP: string = '';
                            const AProxyServerPort: integer = 0;
                            const AProxyUser: string = '';
                            const AProxyPassword: string = ''): Boolean;


USES ssl_openssl, HTTPSend;

//------------------------------------------------------------------------------						
procedure PrepareHTTPSendAsMozilla(AHTTP: THTTPSend);
begin
   AHTTP.UserAgent:='Mozilla/5.0 (Windows NT 6.1; WOW64; rv:51.0) Gecko/20100101 Firefox/51.0';

   //AHTTP.Headers.Add('Accept-Encoding: gzip, deflate, br');
   AHTTP.Headers.Add('Accept-Language: de,en-US;q=0.7,en;q=0.3');
   AHTTP.Headers.Add('Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8');
end;
//------------------------------------------------------------------------------
procedure WriteTextInStream(const AText: string; AStream: TStream);
var
   pText    : PChar;
begin
   pText:=PChar(AText);
   AStream.Write(pText^,Length(AText));
end;
//------------------------------------------------------------------------------
						

//based on Synapse
//For HTTPS-Support:
//  1) USES ssl_openssl;
//  2) copy libeay32.dll
//  3) copy ssleay32.dll

function SendHttpRequest(AHttpRequestType: THttpRequestType;
                         const AURL, APOSTData: string;
                         const AResponse: TStream;
                         var AErrMsg: string;
                         const AHttpUserName: string;
                         const AHttpPassword: string;
                         AAsMozillaUserAgent: boolean;
                         AAnotherHeaderLines: TStrings;
                         const AProxyServerIP: string;
                         const AProxyServerPort: integer;
                         const AProxyUser: string;
                         const AProxyPassword: string): Boolean;
var
   HTTP: THTTPSend;
begin
   AErrMsg:='';

   HTTP := THTTPSend.Create();
   try
      HTTP.UserName:=AHttpUserName;
      HTTP.Password:=AHttpPassword;
      //-- ShowMessage(HTTP.Sock.SSL.LibName);

      if Trim(AProxyServerIP)<>'' then
      begin
         HTTP.ProxyHost:=Trim(AProxyServerIP);
         HTTP.ProxyPort:=IntToStr(AProxyServerPort);
         HTTP.ProxyUser:=Trim(AProxyUser);
         HTTP.ProxyPass:=Trim(AProxyPassword);
      end;

      if AHttpRequestType=rqPost then
      begin
         WriteTextInStream(APOSTData, HTTP.Document);
         HTTP.MimeType := 'application/x-www-form-urlencoded';
      end;

      if AAsMozillaUserAgent then
         PrepareHTTPSendAsMozilla(HTTP);
               
      if Assigned(AAnotherHeaderLines) then
         HTTP.Headers.AddStrings(AAnotherHeaderLines);

      if AHttpRequestType=rqPost then
         Result := HTTP.HTTPMethod('POST', AURL)
      else
         Result := HTTP.HTTPMethod('GET', AURL);

      if Result then
         AResponse.CopyFrom(HTTP.Document, 0)
      else
         AErrMsg:=HTTP.Sock.LastErrorDesc;
   finally
      FreeAndNil(HTTP);
   end;
end;

var
   Mem       : TMemoryStream;
   sErrMsg   : string;
   bOK       : boolean;
   
   iLen      : integer;
   sResponse : string;
begin
   sResponse:='';
   sErrMsg:='';

   Mem:=TMemoryStream.Create();
   try
      bOK:=SendHttpRequest(AHttpRequestType,
                           AURL,APOSTData,
                           Mem,
                           AErrMsg);

      if bOK then
      begin
         mem.Position:=0;
         iLen:=mem.Size;
         
         if iLen>0 then
         begin
            SetLength(sResponse, iLen);         
            mem.ReadBuffer(sResponse[1], iLen);
         end;
      end
   finally
      FreeAndNil(Mem);
   end;

var
   Response  : TMemoryStream
begin 
   ...
   ...
   Response.SaveToFile('response.dat');