MS Access Database on SQL server needing repaired and improved

We have an MS Access Database, where the tables are stored online on an SQL server and the data is updated and manipulated using queries, forms and reports on local computers. This database needs to be accessible, and editable, by multiple users simultaneously and users will require different access rights so that the security of our data can be protected at all times.
One of key database elements - a form with three navigational subforms - is currently not working correctly. The updating, saving and deleting of records on the source table (currently on the SQL server) creates 'write conflict' and 'data in use my another user' errors - even though the database is currently only single user. When the table is taken offline, deleting and updating records becomes possible, but it does not allow users to save a record without creating a new one. The form is also running extremely slowly.
We need a skilled programmer with extensive Access, VBA and SQL server experience to resolve these issues and ensure that our staff - currently working from home - have full functionality of the database at all times. While retaining all of our existing defaults and formatting, we need users to be able to add, update, save and delete records without requiring direct access to the original table, and for the table to remain online at all times. Users should also be able to do this via buttons and require no knowledge of the programme functionality. We would like the existing coding to be examined, and if possible streamlined to improve processing speed. We will also require the programmer to show us how to avoid similar issues when linking to other tables on the SQL server.
There are a number of additional elements that we would like to incorporate into this and other forms, so upon successful completion of this job, there will be the possibility of future work.
We hope to have this form repaired asap, so are looking for a programmer with immediate availability.