I finished Planescape Torment on normal with no problem. i even defeated the last boss in my first ~ 4 tries. But both Baldur's Gate games are so difficult. With the Sarevok fight, i lowered the difficulty to easy, and even then i only killed him because of his crap AI which caused him to lose HP out of his own ally's cloudkill. Now i am playing BG2 and it's so difficult. I am doing side quests to level up for the main quest. My party is level 9. I am doing the Raelis quest and i have no idea how to defeat the bounty hunters in the portal without losing at least 2 characters

As long as you're not stuck you're doing well. If you're stuck post your current party, this will help giving hints.

Some of the side-quests are quite challenging. But there are quite a few to choose from as well. So, if you're finding one too hard, it might be a good idea to either: try a different one and come back to it later; try to progress the main quest a bit more; or try doing the stronghold quests (if you have found your stronghold).

I think also part of your problem may be that you were a bit under-leveled when you finished BG1. It seemed like you hadn't done much of Tales of the Sword Coast, which would have helped. However, if you start a new BG2 game, I believe you start at about level 7, so it should still be do-able. Try a different path, if the one your are on seems too difficult.

Also, bear in mind that the combat becomes more complex and challenging, the higher you go in the levels. The 2nd ed D&D rules are quite complex - if you haven't got high-enough level magical weapons; if you're missing a key countering spell; if your AC is too high/THAC0 too low, it can seem like you're hitting a brick wall at times. I don't know if you've gotten there yet, but dealing with level-draining, gazing and/or mind affecting enemies can be quite tricky.

It takes practice and experience to learn what you need in each situation and how to best balance your party. There are places where you might only be able to handle one combat before having to rest again. Also, use your one-use items. It's very easy to hold onto them too long and end up with a stockpile at the end of the game that could have made things easier.

Are you talking about the battle right when you go through the portal? If so, have Jaheira drop an insect plague first thing.

As I recall there was an invisible assassin type who can one-hit a character. Be lucky with his first hit, was my approach, I think. I don't believe there's time to do any anti-invisible strategy before he does his thing.

If you are talking about any of the other battles in that setting, then they are all set-piece fights where you initiate battle yourself. You can do all kinds of long range stuff. Creative use of fireballs, earthquakes, poison clouds, etc. Or you can go with a torrent of summons.

Also some of the bosses can be lured so you face them one at a time. It's been a while since I played this so my memory may be faulty. I'm sure you can find video walkthroughs of these fights on the 'tube.

One trick that I saw in a video, and which I believe I verified myself, is to cast Wizard Eye,

The spell behaves like a summon spell, but it has some interesting properties:
* The eye is invisible, so only enemies that can see invisible will notice it. However, enemies that can see invisible will notice it, and will attempt to kill it.
* Unlike most summons, the eye will clear the fog of war, allowing you to see enemies and areas of the map before you reach them yourself.
* Furthermore, since you can see those areas, you can order the eye to move independently of your party.
* Since the eye is a summon and not a regular party member, it won't trigger scripts, and hence enemies that would spawn or be made hostile via a script will not be.

It just so happens that the boss in the Astral Prison can see invisible, but the other enemies can not. Therefore, with the Wizard Eye spell, you can actually lure the boss towards your party, and then fight the boss without its companions.

(Minor speed trick: Don't forget that you can cast a spell like Haste on the Wizard Eye to speed it up. While the spell can cause fatigue when it wears off, you really don't care if the Wizard Eye suffers from it, and the Eye will disappear when its duration wears off anyway.)

For what it's worth, I think it's normal if you find early BG2 challenging, partly due to particularly powerful enemies that you can stumble into early on. Not only that, but the planar prison side quest is also more challenging than other quests that you have access to prior to chapter 4. In my case, with some mods that enhance AI and improve encounters, this side quest is actually one of the most challenging to take on before chapter 4 which requires very specific preparation and tons of metaknowledge.