The best way is probably to have a friend/player/coach, but outside of that I’d echo a bit of the above posts: use the “try me” mode and ai to get a grasp of a few heroes before jumping into pvp.
HotS doesn’t have gold – as a resource – and generally doesn’t benefit from last hitting, but it does help to ‘try’ heroes (through the collection) and practice some spell combinations and talent picks on a target dummy to get a feel for range and timing, especially if you have previous experience with other “MOBA”
Some ai games can then introduce map objective variations, but some specific maps can be picked through the custom-games mode and fill slots with ai so you’re not reliant on rng for some map choices. Healers provide more routine healing in HotS than other games I’ve played and they trade that for, conditionally, less killing potential.
Dota & Lol generally dictate the team-role based on gold distribution, but for HotS, it’s mostly based on initial hero choice for tank/initiator, healer/support, and dps. The game-culture generally favors ‘filling’ so people advice learning at least 4 heroes: a tank, a healer, a ranged dps, and then a +1. Since 1 hero is all it takes to get all of the team xp, some levels of play favor having specific heroes do most of the xp collection for a decent chunk of the game while the other 4 players roam, take mercenary camps, or push lanes, so the “+1” could be one of the odd-ball heroes that can play multiple lanes.
There are a few HotS discord servers so you might be able to use their LFG tools to ask someone to assist with pointers or playing out some games since that’s more ‘real time’ than the forums, but I also haven’t used those in a few years myself. Here’s a link for one that seems to still be active if discords are more your jam:
https://discord.com/channels/127283257120129035/127288051293618177
Lastly, regarding meta-gameplay, there is a third-party parser site for checking stats: heroesprofile.com/. Hero popularity and ‘influence’ tabs can help indicate what are ‘powerful’ heroes that may then be more common to encounter, or may indicate a niche expert, or “OP” hero, and potential build-choices for those heroes if you try to counter-pick around those details.