I have found a way myself. It's probably not the most efficient way but I am a random guy having fun with node-red, not a Software developer.
@zenofmud I think it depends on how many packages i will receive so no.
@JayDickson This is how i fixed it. I filtered all the attributes that are always present (friendly_name, unit_of_measurement, icon, attribution). And the usefull data will be filtered with "otherwise" on the switch node.
[{"id":"fab7ae08.18ab9","type":"server-state-changed","z":"3d3f5fac.25e4b","name":"PostNL","server":"cac0837e.bc9b7","entityidfilter":"sensor.postnl","entityidfiltertype":"substring","haltifstate":"","outputinitially":true,"x":129,"y":244,"wires":[["a2999169.d632a"]]},{"id":"ec925256.48edc","type":"comment","z":"3d3f5fac.25e4b","name":"PostNL","info":"","x":129,"y":194.43750190734863,"wires":[]},{"id":"a2999169.d632a","type":"switch","z":"3d3f5fac.25e4b","name":">=1 pakketjes","property":"payload","propertyType":"msg","rules":[{"t":"gte","v":"1","vt":"num"}],"checkall":"false","repair":false,"outputs":1,"x":304.2421989440918,"y":243.4375114440918,"wires":[["1a24f4a9.43fc7b"]]},{"id":"1a24f4a9.43fc7b","type":"function","z":"3d3f5fac.25e4b","name":"Atttributes splitsen","func":"var attributes = msg.data.new_state.attributes;\n\nreturn[{payload:attributes}]","outputs":1,"noerr":0,"x":536.8333911895752,"y":243.66671562194824,"wires":[["4aa1f7e4.eefaf8"]]},{"id":"48048c31.bb49c4","type":"switch","z":"3d3f5fac.25e4b","name":"","property":"payload","propertyType":"msg","rules":[{"t":"eq","v":"Information provided by PostNL","vt":"str"},{"t":"eq","v":"packages","vt":"str"},{"t":"eq","v":"postnl","vt":"str"},{"t":"eq","v":"mdi:package-variant-closed","vt":"str"},{"t":"else"}],"checkall":"true","repair":false,"outputs":5,"x":864.1668510437012,"y":243.6666717529297,"wires":[[],[],[],[],["9388a722.c832b8"]]},{"id":"9388a722.c832b8","type":"split","z":"3d3f5fac.25e4b","name":"","splt":"\\n","spltType":"str","arraySplt":1,"arraySpltType":"len","stream":false,"addname":"","x":1054.0001907348633,"y":240.00004291534424,"wires":[["af1394e9.909098"]]},{"id":"af1394e9.909098","type":"function","z":"3d3f5fac.25e4b","name":"Bericht","func":"msg.payload = \n{ text: `Op ${msg.payload} komt er een pakketje van ${msg.parts.parts.key} `, \nparse_mode: \"Markdown\" };\n\nreturn msg;","outputs":1,"noerr":0,"x":1210.0000343322754,"y":240.00004768371582,"wires":[["d5ebfbd3.0bc0f8"]]},{"id":"d5ebfbd3.0bc0f8","type":"telegrambot-payload","z":"3d3f5fac.25e4b","name":"Versturen","bot":"76d092d0.28022c","chatId":"667099650","sendMethod":"sendMessage","payload":"","x":1381.0000381469727,"y":240.00004768371582,"wires":[[]]},{"id":"4aa1f7e4.eefaf8","type":"split","z":"3d3f5fac.25e4b","name":"","splt":"\\n","spltType":"str","arraySplt":1,"arraySpltType":"len","stream":false,"addname":"","x":728.1667671203613,"y":244.00009536743164,"wires":[["48048c31.bb49c4"]]},{"id":"cac0837e.bc9b7","type":"server","z":"","name":"Home Assistant","legacy":false,"hassio":false,"rejectUnauthorizedCerts":true},{"id":"76d092d0.28022c","type":"telegrambot-config","z":"","botname":"Kevintelegrambot","usernames":"","chatIds":"667099650","pollInterval":"300"}]