Announcement before mention with external purpose

Hello together,
also I am Asterisk a beginner and have the problem which I should realise announcements before mention in which after the announcement the conversation should be passed on to an external participant. This also functions so far, but if the participant was built up to him the conversation (external headquarters) hangs up, the conversation becomes the A participant to him Originally has called not released, the connection stops, to itself hangs up.

extensions.conf

[code]
[default]

exten => _0[1-9].,1,Dial(SIP/${EXTEN}@Rufnummer4090)

exten => 2000,1,Dial(SIP/2000)
exten => Rufnummer4090,1,Dial(SIP/2000)

exten => 1001,1,Answer()
exten => 1001,2,Playback(hello-world)
exten => 1001,3,Hangup()

[MN-IN]
exten => Rufnummer4098,1,Playback(ansage-vormelden)
exten => Rufnummer4098,2,Dial(SIP/0123456789@Rufnummer4098,Ttm)
exten => Rufnummer4099,1,Playback(ansage-vormelden)
exten => Rufnummer4099,2,Dial(SIP/0123456789@Rufnummer4099,Ttm)[/code]
sip.conf

[code]
[general]
port=5060
bindaddr=0.0.0.0
language=de
;allow=all
dtmfmode = auto
jbenable = yes
jbmaxsize = 200

register => Rufnummer4090:PW4090@mein-Provider.da/Rufnummer4090
register => Rufnummer4098:PW4098@mein-Provider.da/Rufnummer4098
register => Rufnummer4099:PW4099@mein-Provider.da/Rufnummer4099

[2000]
type=friend
secret=1234
host=dynamic

[Rufnummer4090]
type=peer
username=Rufnummer4090
fromuser=Rufnummer4090
secret=PW4090
host=mein-Provider.da
fromdomain=mein-Provider.da
qualify=yes
insecure=port,invite
canreinvite=no
nat=yes

[Rufnummer4098]
type=peer
username=Rufnummer4098
fromuser=Rufnummer4098
secret=PW4098
host=mein-Provider.da
fromdomain=mein-Provider.da
qualify=yes
insecure=port,invite
canreinvite=yes
nat=yes

[Rufnummer4099]
type=peer
username=Rufnummer4099
fromuser=Rufnummer4099
secret=PW4099
host=mein-Provider.da
fromdomain=mein-Provider.da
qualify=yes
insecure=port,invite
canreinvite=yes
nat=yes

[IN]
type=peer
host=mein-Provider.da
fromdomain=mein-Provider.da
context = MN-IN[/code]

Does somebody have an idea???

Thank you greeting Christopher