So I main singed and im not bad when comes to dealing counter pics aka(gnar teemo darius etc.) but garen is really rough only because of his ult and its ability to excute with true damage. When he gets this ult it becomes the most stressful lane ever since one mistake ruins u. is there any technique or something that I am missing
Constant slow
Shield when you get it stacked (pop it as he goes to ult you)
Keep him off of you
Later you pick up 
and he takes %hp damage
Rushing armor keeps him from getting you too low.
As long as you're not managing to get any kills outside of lane he won't deal true damage to you either. (killing him doesn't trigger his passive)
Plus Garen's kit is so stupidly easy that it's easy to prediction.
Main thing is that you need to let him push the lane so you can freeze it. Or you can just proxy singed. (don't do it man, it's a trap) You do what Singed does best, you kite all day
You're Singed. run away.
can troll a Garen really hard if he doesnt have true damage on you. Obviously it doesnt fit Singed very well though.
Same strat as Darius, don't get low enough to get dunked when he's around with his ult up.
You cannot deal with Garen effectively, especially during lane phase. You both have good farming mechanics, he just has more kill potential than you. Your best bet is to wait until your jungler arrives to gank. Otherwise, you need your team to kill him because you cannot do it alone effectively. Pick Singed with a team comp that works well with him.
You can attempt to stall Garen's power with and a , and a lot of mobility to keep him off you, but that's the best you can do...
be passive until he uses E. His cooldowns are not that low. thats pretty much it
I pretty much do the same thing in every matchup, go behind the turret as soon as possible and run around being as annoying as possible, matchups don't really matter at that point.
