you blocks are exactly the same as previously...
you already found out yourself, this will not work like this if the app is in the background
as already mentioned earlier
Also your Clock events will not fire and you will not be able to draw something in the background...
You have to do it like this: while the app is in the background, the location data will be stored in TinyDB... additionally you can send your Post requests in the background to somewhere... as an example see the IFTTT setup... just adjust it to your needs and use the keywords as described in the documentation...
Background web properties
The following properties are used to configure the background web functionality to send a request. The following requerst methods are available: GET, POST, PUT, DELETE, PATCH, HEAD and OPTIONS. Also the background web functionality is able to convert keywords into their correponding values. The following keywords are available: DATETIME, URIENCODEDATETIME, LATITUDE, LONGITUDE, ALTITUDE, ACCURACY, SPEED, CURRENTADDRESS, URIENCODECURRENTADDRESS and PROVIDER
you have to setup the web background functionality before starting the locationservice
Later when you start again your app, then read all the stored data from TinyDB and draw on the map... my example project shows you how to draw all the stored coordinates on the map, see the ListPicker.AfterPicking event there App Inventor Extensions: Location Service | Pura Vida Apps
I hope this helps to get you starting...
Taifun