Hello i'm still relatively new too around here
As for your team it's pretty decent for where your are in the game it's just you have a good weakness to water and electric 2 common types and 2 types that are about to be abused by the enemy.
donphan is a great ground type but in the long run golem does better as it gets every move on that set(besides roll-out) plus the ultra rare stealth rock or if you wanna go muscle the mamoswine's route is the way to go(if you do i'd advise switching out either the sharpedo or the manetric for something bulkier to balance it out probably that espurr for the support it can bring to your team or you can backtrack and get magnezone at shades gym)
The delphox is fine but you might wanna grind and replace fire spin with will-o-wisp(47), psyshock for psychic at (51)(after the badge) and think about re-learning shadow ball
It seems you really want to get rid of that noctowl, anyways the golbat is a fine replacement as it gets cross poison and air slash and if you feel like breeding it, brave bird from staraptor. Just remember if you do this you'd be wise to trade out another member for some bulk this time the toxicroak would have to go at least until you get a better fighting type like mienshao or something bulkier like that happiny into a chansey
I pretty much said my piece about manectric already but I find magnezone so much more useful for the type diversity but it's your call just remember if manectric gets out-sped it's a likely K.O. Also magnezone has a better movepool in terms of this game, as manectric move pool does nothing for it and we don't have flamethrower yet, Also ampharos is nice to consider as well because it gets cotton guard which stops physical attackers(you're going to need it for a certain bird)and some awesome rock, bug and electric attack to deal damage in turn
As sentimental as it is that toxicroak is going to get outsourced by crobat and mienshao.
Sharpedo is fine for this point but later down the line (after 9th badge) you might wanna trade it in for a walrein that can lean the ever so powerful and life saving frost breath. I will give sharpedo this for this point in the game it's a great boss killer just see if protect is available in this game
Overall solid just try and get some bulk and a competent support mon(delphox just can't do that role forever)
but that's just my opinion you're free to disregard it and I hope it helps
(Edit) Now that I think about it sylveon can fill that role of tank if you want it to