Long serves

Try to loop all long balls. Learn to loop against bottomspin. 

varghesep, Try getting a partner to duplicate this type of deep serve, varying the location on crossover, BH, and FH - practice looping them.  Once you can hit a decent percentage of these, more frequently try for fast loops right at the crossover or wide FH away from the server.  If you were having a problem returning the majority of this deep bottom/side spinny serve, then you really have nothing to lose trying to decicively finish the point/put the opponent under pressure - you were missing these anyway and giving your opponent free giggles.  When you land them, you give your opponent motivation to try something else, unless he continues to want lose his initiative on the serve and watch his formerly successful easy point producing serves get punished for winners. 

If its long kill it.

In your particular case I would learn to push the long side-backspin serve. Learning to loop these balls will be the next step but it won't be easy for you as pingpongpaddy pointed out above.
Some help on the pushing: As you are training to become a passive player, a push is a good return for you. You want your opponent to loop, but you don't want him to get an easy kill. Your push needs to be long, low and spinny *and* it has to be placed somewhere where your opponent has to move to be able to be in a good looping position. The other important thing about placement is to think how you can restrict the possible angles your opponent can play. It's very important for a passive player to learn to dictate the most likely return in order to be able to position yourself perfectly. This is a huge part of TT, but you'll need a *LOT* of experience to be able to do this effectively. This is one of the reasons why it is not a good idea to try to be a real long distance chopper at this early point in your TT career. It's much better to stay relatively close to the table and try to base you passive game mostly on blocks at this point. Block in a way that he has to move to make his next attack. Block aggressively - not only hold the racket against the ball, but move it forward through the ball and slightly upwards (=wrist action and a bit of forearm). This will get your general level of play up much faster.
Pushing long sidespin from a righty to your bh: The ball wants to go to your right to you opponent's bh corner because of the sidespin. To prevent this, you have to change your racket side angle from this "-" to "/" and then push. An easy way to push these balls is to raise the elbow and make the racket tip point down in the direction of the floor. Now adjust the racket side angle to "/" and push. It's more important to push low and deep than pushing with extreme spin. You have to watch for the amount of backspin and sidespin in the serve. The more sidespin the less backspin will be in the ball.
Good luck.