Is it necessary to implement all that we have learnt in terms of Islamic knowledge?

Will we be sinners if we don’t?

We should try to implement what we can. Allah سبحانه وتعالى does not burden a person more than he can bear, so we should try to implement what we can. If we cannot implement when we are able to, we are sinners, because Allah سبحانه وتعالى has granted us knowledge in order for us to implement it.

The companions of Prophet Muhammad (ﷺ) would never learn beyond 10 verses until they had implemented what they learnt. Once they did, they would go on to the next verses. This is the way we should be (implement whatever we learn) and this is known as the zakat of our knowledge - to implement what we know of the knowledge and to give it to others.

And Allah knows best.