Changing Share ownership

[rks2018]

If anyone an give me some info please ?
I 'm thinking of changing ownership of of my 2 properties , both of which I own 50/50 with my sister though she doesnt really have financial interest in them .
One I live in myself and the other I used to live in. The other my sister lives in together with a lodger , Pay tax on 40% self and hers is 20%
I wish to change ownership to 99% self and 1% sisters . As i am not married yet I wish to do this in case anything should happen to me and wish my partner to be the beneficiary.
I do have mortgages on both which i can now show to afford myself . question is can i do this myself online ? I would need approval from mortgage company I guess.
when I pay SA tax , i then start to pay 40% of 99% of rental ? from date of equaty transfer ?
How will CGT be calculated in future , what values on the house will be used ? Should i get a value before I change % of ownership ?
Thanks in Advance .

[AGoodman]

Can you explain this:

" both of which I own 50/50 with my sister though she doesn't really have financial interest in them "

[rks2018]

yes sorry My sister helped me in purchase due to my earnings at the time , she is named on both the properties .
We are joint tenants in common ? I believe .
thanks