You seem like a welcome addition to the community. Yes you can respec both passives and skills. Yes you can get Warden in the basic mage tree. Keep leveling up and put in the 5 points you want there in Warden. You can put as many points as you want in the base mage tree. You are not limited to 20. You can also remove points in the mage tree above 20 and so on and so forth. You did not need to create another mage due to putting in a wrong passive but whats done is done.
Talk to the chronomancer in either End of Time or the Council Chambers in the Ruined era. You need to have at least 5 points in Tier 1 in the base mage class, then at least 10 points in tier 1 + tier 2, then at least 15 points total in tiers 1, 2 and 3… so how you respec is to put in more points than 20 in the mage passive tree, then take out the unwanted points/ the points you mess up on. What the game wont let you do is take away points in the lower tiers if it means not hitting those minimum numbers I explained above
Tier 1 -Put 8/8 Arcanist , 8/8 Elementalist,
Tier 2 - 1/10 reactive Ward
Tier 3 - 5/5 Mage Flurry
Tier 4 - 5/5 Warden.
Then take out 7 points in elementalist.
TLDR - Keep adding points in the different tiers. Get what you want, then remove the points you dont want. After you finish the first Act, and go to the End of Time you will get a quest upstairs to allow you to choose your mastery class and then you can put the extra points after 20 there. Or you can keep putting in points in the base mage tree if thats what you want to do.
Also…if you ever post like that again I personally wont respond. If there is an ignore feature I will put you on it. Learn to chill out. Your questions will be answered. Just ask them nicely and quit threatening to “%^&*” on the game because you dont understand something.