At 37, I had two miscarriages for my second child. Does it mean if I get pregnant again my child will have down syndrome?

Risk is elevated. As a mother's age increases, the risk of having a child with Down syndrome increases. You can address this with you OBGYN. If you become pregnant, there is a new blood test for Down syndrome which is non invasive compared to amniocentesis.
No, but still risk. Miscarriages are most commonly (about 70-75%) caused by an abnormal number of chromosomes in the pregnancy. Downs (3 chromosome 21s) is one of the most common chromosomes to be abnormal. Still, the risk of a live-born child with downs is about 1 in 217 (age 37) and 1 in 166 (age 38). If you have multiple miscarriages then see a specialist to discuss testing. Best wishes.
No. While most miscarriages are due to issues w/viability, there is no association between miscarriages and down syndrome, which is a genetic condition more closely linked to maternal age. Best to go see your family physician or OB for pre-conception counseling to determine your individual risk for trisomy 21. Testing can be done early in pregnancy to find out if your baby has health concerns.
No But... It is certainly a possibility, but a higher probability that down's will not happen. No guarantees.