If the bass has roundwound strings and your technique isnt flawless then you are going to get these string noises.
There are a couple of solutions.
Change the strings to flatwounds or half-wounds. The sound will be different overall with the flats, deeper,less harmonic content, purer notes,and a noticeable lack of string noise. The halfs will be similar to both sets and the string noise, while muted, will be back somewhat.
Another solution is to get a piece of thin flexible foam padding and roll up a piece and fit it under the strings at the bridge. Use a thick heavy pick and attack below the soundhole. This will give you that time-honored 'thunk' sound you have heard on so many recordings throughout rock history and will quiet the string noise, though it will not remove it.
The best solution if you like the sound of the round-wound strings is to perfect your fretting and plucking technique.
In short, become a better player.
It takes time and patience. It takes dedication and practice and while there may be a short-term solution to this, all are compromises compared to becoming a player with quality technique and chops.
They also make a rubber damper which goes in the soundhole. It may stop a bit of the noise but everything thats coming from the fretting is all about you and how you play.