Procedure expects parameter '@statement' of type 'ntext/nchar/nvarchar'

Here is one of the possible solution:

Convert your @sqlstr to varchar(max) and instead of EXECUTE sp_executesql, use EXECUTE(@strsql).In this fashion you got your complete print query and it will also execute your query.Hope that it helps.

Declare variable as a nvarchar type when you are using command exec sp_executesql.Above you used varchar for @sqlstr variable.
Eg.

Declare @Sqlstr nvarchar(max)
SET @Sqlstr='...Your dynamic query...'
exec sp_executesql @Sqlstr

Note:Dont use brackets in exec command

sp_executesql takes NVARCHAR as parameter not VARCHAR, change varchar(max) to nvarchar(max) will fix the problem.

DECLARE @sqlstr AS  nvarchar (max)