… I have tried inserting systems but the layout of the systems before and after are affected …

1) You should Lock Systems before you insert the new movement.

(Selection Tool, Select All, Utilities menu > Lock Systems)

Also, you should perhaps insert a Page Break at the beginning of each movement, and perhaps also at other places.

(Page Layout Tool, click to select, Page Layout menu > Insert Page Break)

2) To delete / insert systems, do not delete / insert measures.

Instead, use the Page Layout Tool, to delete / insert systems:

Page Layout Tool.

Click to select.

Page Layout menu > Delete Staff Systems

Page Layout menu > Insert Staff Systems…

1) You should Lock Systems before you insert the new movement.
(Selection Tool, Select All, Utilities menu > Lock Systems)
Also, you should perhaps insert a Page Break at the beginning of each movement, and perhaps also at other places.
(Page Layout Tool, click to select, Page Layout menu > Insert Page Break)

 
2) To delete / insert systems, do not delete / insert measures.
Instead, use the Page Layout Tool, to delete / insert systems:
Page Layout Tool.
Click to select.
Page Layout menu > Delete Staff Systems
Page Layout menu > Insert Staff Systems…

Actually number one 1), should be make a copy and work on it. I would rename the copy, too. Its a good idea to have backups being made as you save along with 10 min. autosave.