Gardening advice regarding bush and fence posts

I have a bush in my garden and the flowers have died and it's all brown so I cut it back or wait for it to grow back in the spring?

Also I have some family helping put fence posts back after the fence came down the post one is short one is too long I'm hoping I won't notice but could I glue a small bit on do it looks level and paint it?

 

One more question how would I go about removing white marks from slabs?

 

Do you know what plant it is? With some plants the dead growth is best left in place to provide some protection over winter,

You can get metal fence post extenders with have a fence post sized socket at each end.

Is it efflorescence? (Google it for images)? If so there's some previous threads on how to deal with it.

 

Uploaded a picture of the bush here

The only issue with the metal extension is the posts are cemented into the ground now so that may be an issue?

 

They are used at the top of posts, to extend to a higher level.

That's the plant I was mainly thinking about.

 

Have a look at this link (which includes photos) for how to care for and prune Hydrangeas.

This link shows you how to extend a fence post.

 

I have cleaned the slabs using a small wire brush however they look all scraped and it's not removed all the marks but some.

Is there any way to restore them or buy another cleaner what else could I use?