end of chapter 1 i need to fight letho (the assassin), no matter how hard i try cant defeat him. thoughts?

Same.

What difficulty are you playing on? What skills have you leveled up? Can you believe it's not butter?

The answers to those questions would inform a specific approach to take. Generally speaking, however, spamming Yrden and rolling like a mofo seems to work.

Level 10, two points availible. I have Riposte, and nothing in any of the other trees, besides "basic witcher training"

Where should I put those points?

If you have upgraded Quen, it's quite helpful in this fight, too.

I managed to kill Letho using only it and the sword.
The key is to get slightly out of phase with the opponent, so that his Quen field ends when yours is still active, he hits you, gets zapped, and you hack away.
The only hard part is tumbling away in time to recast your own field.

you should use aard i would say since he can break it in one shot and takes time to use quen.for mid lvl fast and strong style sword work will do the job.dont let him hit you cause in that level you are heavily disturbed when attacking.

That's pretty much exactly what I was going to post, except I threw in a few Yrdens, just to try to speed things up.

Try not to get too close when your Quen isn't active, but be aware that if you're too far, he'll start shooting Igni and throwing bombs at you.

I use just swallow, and only yrden sign beat the boss after countless loses. Everytime i get a little closer to beat him. Anyway thanks a lot

I just turned it to easy for that fight; was cake, then I went back to normal.

Throwing Daggers can also be used to stun-lock him even when his shield is up.

if u change the difficulty, do u still get the same experience?

Found this fight pretty tough the first time but after many attempts and a night sleeping on it i finally beat him with a heavy attack, heavy attack, arrd push , heavy attack heavy attack and dodge away. worked pretty well but you have to time it right and get out of the way if he blocks also dont stand around if he shields up just roll/run around until shield runs out avoiding bombs and signs and then attack again. its not perfect but worked for me in normal. in hard (2nd play through) i had changed my skill tree choices alot and i had my shield upgraded twice and also had 2 extra vigor bars and found it alot easyer cause i could shield up and just hit him with hard attacks alot. just learn to time your attacks and also how to roll so that you face him again roll back, roll left amd roll forward attack. it takes practice but can be done ( also as per spoiler i fought him with my 2nd best steel sword the 2nd time round) ** also theres a health power point at the bottom of the path that leads up to the rose garden if you activate it and then go into the fight you get 3 mins of extra healing :D