Transmision rough shifting ( 96 aspire )

My 96 aspire shifts very roughly from gear 1 to 2 during acceleration. Also when driving 80km/h or more sometimes a strange rattling noise
comes from under the car and feels like the car is loosing power. Is this a major transmission problem? I check the transmission fluid and it seems to be ok. Is there something a home mechanic can do before going to the professional shop?
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