My baby girl is 11months old with trisomic21 downsyndrome and is not sitting as yet need help?

My girl has a trisomic 21 downsyndrome she is 11months old now but is not able to sit byherself or attempt to stand or crawl byherself,is there anythng that I can do to help her improve? Otherwise she has quite normal features and she also turns,and speaks words like dada,mama,papa ,tries to immitate what she finds of interest to her like some funny lip movement,funny sounds,she attempts to be quite active when we are talking to her ,listens,shows gestures like holding your finger if u bring it towards her,responds when u call out her name and so on...

[Mglos]

Take the cushion off couch sit her down and put cushion on her lap .put some toys in front of her to play.also  keep her on her belly as much as you can .to play or watch tv. You need to build her upper body strength up.stop carrying her around ...she'll try harder to move and will eventually crawl wich is very important for her hips to crawl. She needs to gain strength that's all.do you have early intervention? Get it if you don't. Get some books on babies with ds there helpful. Ds kids do things at a slower pace than regular kids.