Should I start over ???

"Knowing what i know now and with some luck i could potentially have a x2 better team..."

This is the reason why I wouldn't suggest doing so. You never know just how much "luck" you'd have in summoning. Spending hundreds of orbs for a "bad IV" unit, or a pity-breaker of a unit you don't want (Merric) can really screw things up, especially if you go from "I have a lot of good units and being pity-broken" to "I'm restarting and was pity broken"

Of course, you can also have good luck, too, but that's up to RNG.

Anyway, it's up to you, but I'd probably keep the current roster if I were in your shoes. You have a lot of 5* units that aren't easily obtained (seasonals like W!Robin, S!Kagero) and some that'd take some luck to even pull (Delthea, Amelia, F!Celica...).

I wouldn't. You won't have any of the GHB or TT units, and your roster looks too good to give up. It's also funny to look back on your units and go, Why did I do that?

Dont, just keep going.

just because yuou made some bad investements doesnt mean that you need to throw out everything. you have a lot of stuff that looks good and can be useful too in some way. if you start over, there's no guarentee that you'll get anything good. and no matter what, it seems like quite a waste. We all make dumbass mistakes in this game

How could you get 2x better units? You don't get all your orbs back when you make a new account.

Sorry I dont quite understand what your asking, If your saying should you start a new account....no...absolutely no

You should just start using the units you have and like and optimizing them, and fodder off the units you have built that dont fit in your long term builds

If you have become a consistent top tier arena player since December without spending any money on the game, I wouldn't consider calling it bad investments or nonviable builds. On the contrary, you seem to have taken what you've learned and ran with it.
In addition, there is no guarantee that you will have a better team. That's the beauty and curse of FEH: every person has different units and teams due to RNG. However, that's not to say that differences are bad;in fact, it can serve as the building block for adapting and tackling difficult characters with the options you have.
I won't advocate a specific choice, but instead ask the question of whether you are willing to sacrifice five months of building and investing to have a completely different team.

You will not be recovering the orbs obtained from events nor any of the TT units, (or the feathers, medals, refinement stones...) and we don't know when some of those GHB units will be back either. So... Don't. Throwing everything away would be a waste.

Also, if you are a consistent top tier arena f2p player your choices can't have been that bad.

Having said that, there is nothing stopping you from making an alt.

Unless those armors and dragons have a bunch of breath and fighter skills on them, starting over would be a good idea. That roster is nothing impressive and can easily be built up again. You get around probably close to 700ish orbs (very rough guess) from the main story quests and a guaranteed top tier hero from reroll. You also get access to the hero fest banner for steady breath. Roll on a good legendary banner and with some luck (obviously) you can build a good team up fairly quickly. You also don't seem to have that many merged units so it would be even faster to transition.

And to the people talking about TT units....who cares, they are garbage anyways.

This came decision came upon me as well and I did do it. I have been able to create better teams and have been able to stay in tier 20 in my new account but I regret just deleting my old one. I had many units that I currently miss. I suggest having 2 accounts by saving each to a different nintendo account (do not delete data btw). You can still restart, but you can still go to your old one if you want. It only takes about 10 minutes to switch between accounts so I wish I had did that.

I don't think that it's worth throwing away nearly half a year's worth of work to start fresh. There are a lot of good units in your arsenal, and a lot of them are rare/limited, really good, or top tier.

You also mention that you were able to hit Tier 19, which is honestly an accomplishment considering the amount of time playing. (For reference, I wasn't able to stay consistently in Tier 19 until 8-9 months into the game.) It doesn't matter which mistakes you have made, as I'm pretty sure a lot of players (myself included) made plenty up until this point but kept on playing without starting over.