1. Is this a good time to build crypto portfolio?
Actually, you will always have a good time building your own portfolio as long as you know the right coins to buy. Sometimes, there are many coins that are likely legit, but in fact, they are only hype and will only utilize pump and dump. I think that building a portfolio in this kind of market will be better to start with top coins, that have good and strong fundamentals and also don't reach their ATH yet. It may still have a chance later.
But, once more, DYOR, none will guarantee.
2. Do you really think that bear market will be a dipping as 2018?
There will be always a cycle where a bullish and bearish market will be changing due to a certain period of years. And every period has its own dip price at the breakout.
For later bearish, hopefully, there will be not as dip as in 2018. And if seen from the highest rate of Bitcoin so far, it should not be as dip as in 2018.