I build a retaining wall, and used a level to ensure that the baseline brick was gorunded even with the gravel.
I glued the third brick base to the second, and have already glued the toppers with construction adhesive.
The retaining wall is elevated higher on the left side and if you view the image below, you can see the slope from left to right.
I'm not sure how to fix this now that I've glued this up. Any suggestions?
There is no good news if you wish to level it.
Except for the cap stones, there is no real good reason to glue them down.
You will have to remove everything down to the gravel/sand base and do it again.
You MUST check level every time you put a block down,
I use a four by four and a four pound mini sledge to hammer them level. I if it gets cock-eyed check your base. If your base gets too compacted you have to add to it check level and then, gently, no harder than necessary hammer it level. You then take a long level and measure across three blocks.
You can scrape the glue off and as I said except for the cap stone there is no need to glue them.
How thick is the base gravel?
Was the ground under the gravel solid or soft?
Was the base ground semi-level before you put gravel on it?
Do not lay on gravel, put sand, and inch or so on top of the gravel and set your blocks on that.
Gravel will not level due rocks.
I did this for a living for years and it takes practice to get a feel for it.
Check your level, then check it again, then check it again without stopping every time you lay a block.