Review

Repair top of garden concrete wall

We have quite a large concrete retaining wall, I am not sure how clear it is in the photo but some of the top has cracked off, so uneven. We have also now put a wooden plank behind the wall to keep mulch and mud in area. We want the top of the wall repaired and also wondering whether it should be plastered together with the wood, or filled somehow so that weeds don't grow through the gap. Keen on getting a quote on this job, and what options are available. I am not entirely sure what type of tradesman would do this work.