Hi, my name is dowdy

PIP is not about the conditions you have but how they affect your ability to carry out a range of essential daily tasks and your ability to walk outdoors.    And 50% (at least four a week) must be bad days when you have great difficulty carrying out these tasks and walking outdoors.  

If possible, try to get some face to face advice from CAB or a similar advice agency.

At assessment, it's a good idea to keep answers as simple as possible without excluding any essential details.  Assessors are not very highly trained medics (mine was a paramedic) so probably will understand little, if anything, about your condition itself. 

The assessor will also observe you informally and ask you indirect questions that indicate ability to carry out tasks.  For example, they'll observe you walking from the waiting area to the interview room, watch if you put any belongings down on the floor and pick them up later, watch how easily you are able to take a coat off and put it on.  And they'll ask if you have any hobbies - for example knitting or doing jigsaws would indicate a high level of manual dexterity.  They might also ask if you do housework which would indicate considerable strength and stamina.  And if you have any pets which would indicate a certain recurrent ability to be active in order to look after them.

This link is the DWP's guide to assessors about how to informally observe interviewees and how to indirectly ask about the extent to which they are active.

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/547146/pip-assessment-guide.pdf

Below is a link to the PIP handbook that tells assessors how they should conduct assessments - but assessors don't follow all the rules!

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/519119/personal-independence-payment-handbook.pdf