There are different conversion kits; Bafang have both mid drive kits (motor at the crank) and hub kits (motor at the rear). Some companies do front hub kits, I don't think Bafang do, and you probably wouldn't want one on that bike anyway. The bike looks fine for a crank or rear hub conversion.
With the rear hub kit you should be able to keep the gearing unchanged.
With the crank kit it will probably come as single speed on the front, but you can often manage double front change depending on chainline details.
Hub kits are generally simpler and cheaper than crank kits, and have less wear on the transmission. They are generally best for commuting, pleasure riding and basic off-road riding. Crank kits are better where there a very steep hills, and for more technical mountain biking. Reliability is about equal for both, but fixing any issues that do arise tends to be simpler for hub kits.
If you haven't already, look at
https://www.pedelecs.co.uk/forum/forums ... ussion.42/ and the other forums on that platform.
The Bafang kits are good but so are lots of the alternatives. I'd recommend Woosh as a supplier because of their excellent customer service.
https://wooshbikes.co.uk/ Especially for a first time conversion; they'll check out details of the bike and how you expect to use it before selling you something to make sure it's suitable, and give you lots of advice on fitting or with subsequent issues.