yes i understed all of that? so what is next?

now what do you what me to do?

OK here is what I suggest. How about you try an example like  5.7 + 3.6 and see how you get on with that.

OK here is the problem:
 
  5 .  7
  3 .  6
--------
--------
What is the first step in solving this addition ?

Yes well done. Correct.
Right how about 3.57 + 6.69 ?

3 .  5  7 +
6 .  6  9
-----------

-----------  ???

If you had three things to add together like 1.78 + 2.89 + 3.67 what would you do ?

Yes so you could put them all in one addition if you wanted. Like this
1 . 7 8
2 . 8 9
3 . 6 7
---------

---------

I have noticed that you are quite good at these sums. Are you okay with 10.69 - 8.78 ?
Do you want to have a go at that one ?

Right first let's write it out in full:
1 0 . 6 9
    8 . 7 8
-----------

-----------
Now the first bit is easy. 9 - 8 = 1.
So in the answer the number one can be written straight away.
1 0 . 6 9
   8 . 7 8
-----------
           1
-----------
Now in the next stage 6 - 7 = -1 this is a problem because we need a number between
0 and 9. I would then look to the left of the top number. In the next column there is a "0".
This is no good: We cannot decompose a zero.
So: Look at the far left at the top. We have a one so we can take 1 away from this to get
zero. Then we can drop off a "9" in the next column to the right. Then drop off a "10" to
the right of this (notice that we are just redistributing the number here - 10.0 = 9.0 + 1.0).
  9 . 16  9
  8 .  7   8
------------
             1
------------
Right I will give you a minute to look at that and ask any questions about that bit....

Right now the subtraction can be done quite easily:

9 . [16]  9 -
8 .  7     8
-------------
1  .  9     1
-------------
By the way I need to mention a few points before I teach you any bad habits.
There are limits to what I can display at this speed, online via a maths forum.
I have had to adapt the way I would usually write subtractions considerably.
If you have to attend an exam on subtraction (and other topics) then please follow
the conventions in your course about how to present your answer.
When I was taught how to do subtraction I would cross out the "1" and put a zero
The "0" to the right would be crossed out and replaced by a 9.
The 16 would be written with the "1" superscripted slightly to indicate that it had been
put in afterwards etc. Method marks are often more important than getting the correct answer.

OK. How about you try  20.37 - 18.66 ???
Try to indicate how you worked out the answer as well as you can.
There are limits to what you can do in plain text.
I will probably be able to see if you have used a sensible method.
Good luck.

Very good.  Correct answer.
Can you see how to do 5 .69 - 3.78 ?
If you can do it then go ahead. I wll explain it if you need help.

Another one you might like to try is: 1.3 - 0.716 ?
Notice here that the decimals are not the same length so care is needed with positioning
and place value.