My major is biomedical engineering, mainly researching and developing medical equipment.
note:
1. The sentence "developing medical devices" contains grammatical errors (developing) and spelling errors (developing medical devices), which should be "developing medical devices".
2. "Medical equipment" is translated as "medical equipment". References:
china international medical equipment fairb
The first sentence is translated in the order you provided and can be used. The second sentence is more authentic English.