Living in '21st' (generalnie piszemy XXI) century 'is' (to tutaj nie pasuje, bo pozniej masz 'may be') for many people may be a hassle, 'it is known' (przez kogo? dowody?) that 'in times which we are living in' (jest takie slowo 'contemporary' zobacz czy ono by pasowalo lepiej), (brak przedimka) world keeps on 'moving forward' (to znaczy gdzie? czy jedzie po autostradzie? napisz to inaczej) which causes many sacrifices, one of 'those' (zle slowo, tutaj 'these') are (przedimek) decisions of spending life with ANother person and starting a family. (To zdanie wg mnie jest troche za dlugie). Many people 'tends' (nie, tutaj masz 3os.l.poj, a 'people' to l. mnoga) to wait after their 30s before deciding about those aspects in their lives which from my point of view have their positive and negative points.
First of all, people 'which' (jak piszesz o ludziach to zawsze WHO) (tutaj brakuje slowa 'have') decided to start their own family after (brakuje 'their') 30s, are more 'expirienced' (blad ortog.) in life in general which grants them (przedimek) ability to encounter more issues within their lives that may 'overhelm' (ortog) younger ones 'that' (ja bym tutaj dala 'who') made (przedimek) same decision. Secondly (daj tutaj przecinek) it is 'belived' (ortog) that older people are often financialy independent that 'gives' (dla mnie nie za trafne slowo) (przedimek) strong ground in starting (przedimek) new family, younger ones 'are having' (daj tutaj 'have') problems with this aspect and 'asking' (ask) their parents for help. Another point is THAT being mature 'itself' (niepotr), it is easily noticed how often young ones are breaking up with their partners which may be caused by (ja tutaj okreslilabym te emocje, np. strong, immature) emotions. On the contrary elders appreciate love and if something does not work out they 'are trying' (uzywasz zle czasy, wystarczy simple - try) to fix it.
No matter how convincing may be (przedimek) arguments listed above, every decision in our lives 'have' (decision-it-3os.l.poj, pamietaj o koncowkach czasownikow) bad sides. One of those is the fact THAT the decision about starting (przedimek) family later itself does not guarantee us anything, for (przedimek) person that 'spend' (person-he-3os.l.poj, uwazaj na to) THEIR whole life on (przedimek) education and (przedimek) career it may be quite a big 'challage' (ortog) to meet (przedimek) person of the opposite sex and establish (przedimek) relationship with them, due to (tutaj brakuje slowa, daj 'their') low social skills. It 'has to be known' (nie, to jest za silnie, uzyj moze 'it could be argued') that (przedimek) independent older person may come to (przedimek) conclusion THAT they do not need to start (przedimek) family, from their point of view it may cause many problems which are unnecessary for example 'rising' (zle slowo, podobne ale nie to) (przedimek) own child(,) (niepotrzeba tutaj przecinka) 'that' (niepotr) may cause loneliness in their life that sooner or later will lead them to depression. (brak przedimka) similar effect may be caused by postponing (przedimek) overall idea of starting (przedimek) family after our 30s, it is because we are not always 'sucessful' (cos to slowo wydaje mi sie blad ortog) in our lives and it is good to have (przedimek) family that 'are giving' (nie, uzyj simple - give) us more motivation.
I strongly 'belive' (ortog) that arguments on both sides have really convincing points, I can hardly choose between one of them, but I feel that, starting (przedimek) family after being 30 years old, would be better because I 'belive' (ortog- podam Ci to - believe) that I have to learn to live 'with' (czy masz na mysli 'by'?) myself first before living with someone (dodaj slowo 'else').
People 'are saying' (lepiej 'say') that love can not be 'compelled' (cos dla mnie nie za trafne slowo) afterall.
Uwazaj na te przedimki (a, an, the). Uwazaj na koncowki czasownikow 3os.l.poj.