How to use custom data from RSS feed?

I’m trying to import events from another site I’m hosting and I have created custom RSS feed to import from. The structure of the RSS I’m importing from is like this:

<item>
<title></title>
<category></category>
<link></link>
<pubDate></pubDate>
<startDate></startDate>
<endDate></endDate>
<startTime></startTime>
<endTime></endTime>
<locationName></locationName>
<locationAddress></locationAddress>
<locationPostcode></locationPostcode>
<locationTown></locationTown>
</item>

For some reason WP RSS Aggregator still uses the same Published date for each item and that seems to be the date when the item is imported.

I need to print out the event startDate and title with a link to the original event on the other site. The title with a link works like it should but I can’t figure out how I would import the event startDate data with WP RSS Aggregator.

I would like to get the startDate imported and use it for sorting the events by nearest start time.

Well the source feed actually has the correct order already and it removes events from the feed after the date has passed. For some reason I just can’t get WP RSS Aggregator to sort the feed the same way the original is sorted.

Even if I’m using the setting “Original feed order” WP RSS Aggregator just imports the events in a random order.

You can see the custom RSS feed here: https://oripaantapahtumat.fi/tapahtumat/feed/

startDate and pubDate are the same for each event.
WP RSS Aggregator prints out the date when the events were imported but I want to print out the startDate data. How do I do that?