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Yes, uploads can help dramatically with downloading.

Remember you can only download as fast as the person(s) at the other end can spare. This can vary from day to day. You might also be downloading from a partial file sharer; a person who does not themselves have the complete file but shares as much of it from their incomplete folder. This helps increase overall download speeds when Partial File Sharing is enabled.

I always re-search a topic & then 'Get More Results' function to in the hope to find more sources to download from. Uploading similar material often seems to help 'finding' more sources when you are searching.