Hi all, also new here...
First of all, trying to defeat the Odessa Campaign in Hard straight from the beginning deserves the respect from all of us
Now, I remember defeating that mission in Normal, by taking the boat (forget about that T-something-amphibious useless piece of junk) and disembark on the right beach (the one close to the front line). Then sneak your way to the 2 pieces of artillery close to the coast line. There are few Romanian troops guarding the guns, but it should not be too difficult to take them out.
Then using the artillery, shoot everything that moves, starting with the incoming armours.
Also, I should advise that you really should try to keep your sabotage crew entire, otherwise storming the artillery and facing the incoming Romanian would be tough. Also try to move swift, so the enemy attention would be draught to their front line.
In general, I find RT even harder than MoW. Finishing everything in "Hard" will be ... hum... challenging