how can I upload my imported data from the past? I already downloaded it.
Open it in a spreadsheet app, open sheet "10_listeningHistory" at the bottom and delete all unnecessary columns keeping only the important ones. Then sort it up- or downwards by column I "Date" (here upwards with oldest track first) and save this sheet under a new filename in CSV format, as the rest of the personal data is not necessary.
This new file should be imported in the Last.fm Scrubbler, the individual columns for artist, track etc. have to be adapted in its settings. "Listening time" in seconds is only necessary if you want to set individual track lengths for each imported track. And the original "Date" cannot be used either when importing old scrobbles, as they will have to use the current date of import anyhow due to the 14-days age limit on Last.fm for imported scrobbles. Then check the preview in Last.fm Scrubbler before importing, also you should not import more than 3k scrobbles per day, otherwise your account will be blocked for 24 hours.
Note that I haven't tested this myself, so this is just a suggestion how it could be done. Maybe using a new test account for this makes sense, too, before ruining your real account with it.