When I read this it was 8:27PM so I opened up my PC version of the game and saw I was currently at tamer rank 6 with maybe 100xp in that level at most. So I timed myself and ranked myself up to lvl 8. By the time I finished, it's now 8:56PM on the same night.
I genuinely don't mean this to be rude, but either your estimations are really off or it's just a skill issue. I'm not sure what else to say other than that.
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Here's some advice. Make sure you've spoken to Komondomon (he will eventually spawn in village of beginnings) to unlock the ability to open new areas.
Once this is done, speak to the Leomon in Village of Beginnings (upper left corner) and fight him to unlock Dina Planes.
While at Dina Planes, look for golden acorns to spawn in the trees. Fight some digimon or catch fish while you wait. Get three in one go if you can. Once you've gathered at least one acorn, you will find Dracmon at Log-In Village.
If you give three golden acorns to Dracmon, he will unlock challenge mode. I literally leveled up from rank 6-8 in 30 minutes by grinding off the easiest challenges.
Hope this helps!