"I send them long and beautiful messages."
Translation:Lor le trimit mesaje lungi și frumoase.
Romanian is very flexible. The following are both valid and have the same meaning:
- (Lor) le trimit (eu) mesaje lungi și frumoase.
- (Eu) le trimit (lor) mesaje lungi și frumoase.
However, without enough context, for them to be equivalent to I send them long and beautiful messages. I would argue that eu should not be optional because ei could be used instead changing the meaning to They send them long and beautiful messages.
You are correct. This topic is difficult in duolingo as these sentences do not translate very well into English. You really need someone to give the proper emphasis verbally to convey their true meaning. The closest English in written word is to say "I give them" or "I give THEM". Romanian has extra tools to give a more picturesque version of what is happening.